Click the link to read the article on the Colorado Climate Center website (Peter Goble):

March 14, 2025

Thursday, March 20th marks the spring equinox – the first day of spring according to most calendars. But does spring really start on March 20th? I would argue the answer is “yes, no, and maybe.” March and early April is possibly the most confusing, yet most important time of year for Colorado climatologically.

Three Ways to Define Spring

The start of spring may be defined in several ways:

Astronomical Spring uses the sun’s position. The astronomical calendar divides the year using solstices and equinoxes. Our summer solstice occurs when Earth’s northern hemisphere’s tilt towards the sun is maximized. Our winter solstice occurs when Earth’s northern hemisphere’s tilt away from the sun is maximized. The spring equinox (late March) and fall equinox (late September) occur when Earth’s tilt is tangential to the sun, resulting in 12 hours of daylight everywhere.

Climatological Spring is simply the three-month period of March, April, and May. This definition doesn’t follow Earth’s orbit but aligns better with our temperature experience. Astronomical seasons can be counterintuitive: December 19th is fall, but March 19th is winter? Yet March 19th is typically warmer than December 19th in mid-latitude locations.

Phenological Spring focuses on natural changes – new grass, blooming flowers, and leafing trees. The National Phenology Network tracks leaf-out dates using satellite data. The 30-year average for the Front Range (Fort Collins to Colorado Springs) is between April 1-15. In eastern Colorado and southwestern valleys, it’s March 15-31. In the high country, it might be as late as May or early June. The phenological processes of spring vary yearly based on weather conditions.

Beyond These Definitions

These three definitions do not cover everything. Farmers might define spring by planting time – commonly late April or early May in Colorado. Others may focus on when snow stops falling. On average, the Front Range sees its last snow around the third week of April – earlier for the eastern plains and southwestern valleys, but much later for the mountains. Some areas, like the aptly named “Never Summer Range,” may see snow year-round. As recently as 2019, even the lowest elevations of eastern Colorado had snow as late as May’s fourth week, disrupting graduations, weddings, and “summer break” plans.

Alternative Approaches

I might define spring on the northern Front Range as starting when the average minimum temperature rises above freezing and ending when the average daily maximum temperature hits 80°F. PRISM data shows this works reasonably at lower elevations but less so for higher ones.

Climatologist Brian Brettschneider suggests defining winter as days in the bottom 25% of the temperature distribution, summer as the top 25%, and spring/fall as everything between. By this measure, Denver’s spring begins in March’s third week and ends in June’s second week. Check out his blog for more details.

The Fifth Season?

If we define spring phenologically using leaf-out dates (late March/April or later in mountains), what do we call mid-March? With sunset at 7:00 PM and warming temperatures, it doesn’t feel like winter, yet spring’s phenological processes have not begun. Perhaps it’s a fifth season – “wind season” (Colorado’s windiest time) or “water season” (crucial for our state’s water supply).

Colorado’s Most Important Season

This transitional period is extremely important for Colorado. Most of our usable water comes from mountain snowfall that melts in spring and flows into reservoirs. April is the wettest month for much of our high country, with March close behind.

When March and April are dry, mountain snowpack suffers and snow melts early. When they’re wet, snowpack is likelier to peak at or above average, and snowmelt comes later. This shortens our high-elevation fire season and leaves more water in our reservoirs through summer and fall.

So while we debate whether it’s technically spring yet, remember that March and early April – whatever we call this season – plays a crucial role in Colorado’s water security and ecological health for the entire year.

Click the link to read the article on the Grand Junction Daily Sentinel website (Dennis Webb):

March 9, 2025

Statewide snowpack, which becomes spring runoff that serves agricultural and municipal needs, stood at 90% of normal as of Friday morning, according to the Natural Resources Conservation Service Colorado Snow Survey program. Accumulation amounts continue to show a distinct north-south split. Northern basins are performing better as is typical in winters such as this one that have La Niña climate patterns marked by colder-than-normal surface ocean temperatures in the eastern equatorial Pacific Ocean.

Snowpack in the Colorado River Basin headwaters in Colorado stood at 101% of median as of [March 7, 2025], the Yampa-White River-Little Snake basins were at 96% of median, and the South Platte Basin was at 106% of median. Farther south, the Gunnison River Basin was at 89% of median; the Arkansas River Basin, 76%; the Upper Rio Grande Basin, 66%; and the San Miguel/Dolores/Animas/San Juan basins, 69%.

Grand Mesa continues to lag behind in snowpack levels. An NRCS measurement station at Mesa Lakes shows snowpack at 81% of normal, but the Park Reservoir and Overland Reservoir stations farther east are at just 69% and 66% of normal, respectively. The current streamflow forecast for this spring and summer at Surface Creek at Cedaredge calls for flows of just 57% of normal.

Click the link to read the article on the NOAA website:

March 12, 2025

February Highlights:

• Temperatures were above average over much of the globe, particularly in the Arctic, but much below average over western Canada and the central United States.
• Global and Arctic sea ice extent ranked lowest on record for February.
• Twelve named storms occurred across the globe in February, which set an all-time record for the month.

Temperature

The February global surface temperature was 2.27°F (1.26°C) above the 20th-century average of 53.8°F (12.1°C), making it the third-warmest February on record. According to NCEI’s Global Annual Temperature Outlook, there is a 4% chance that 2025 will rank as the warmest year on record. 

It was the fourth-warmest February for the global land air temperature and the second-warmest February for the global ocean surface temperature. Global temperatures have cooled in recent months as a La Niña episode, the cold phase of El Niño Southern Oscillation (ENSO), developed. Global temperatures tend to be cooler during periods of La Niña in comparison to periods with an El Niño present.

February temperatures were above average across much of the global land surface, particularly over the Arctic, central Eurasia, southern South America and central Australia. Much of western Canada, the central United States, eastern Europe, the Middle East and China were colder than average. Sea surface temperatures were above average over most areas, while much of the central and eastern tropical Pacific was below average (consistent with La Niña), as were parts of the southeast Pacific, western North Atlantic and the northwestern Indian Oceans.

Snow Cover

The Northern Hemisphere snow cover extent in February was slightly below average. Snow cover over North America and Greenland was below average (by 50,000 square miles), and Eurasia was also below average (by 40,000 square miles). Areas of below-average snow cover include the central United States and much of Europe.

Sea Ice

Global sea ice extent was the smallest in the 47-year record at 6.16 million square miles, which was 770,000 square miles below the 1991–2020 average. Arctic sea ice extent was below average (by 430,000 square miles), ranking lowest on record, and Antarctic extent was below average (by 340,000 square miles), tied with 2022 for third lowest on record.

Tropical Cyclones

Twelve named storms occurred across the globe in February, which set an all-time record for the month. A record five named storms occurred in the southwestern Indian Ocean. Five named storms occurred in the Australian region, as well as four in the Southwest Pacific.

---

For a more complete summary of climate conditions and events, see our February 2025 Global Climate Report or explore our Climate at a Glance Global Time Series.

Click the link to read the report on the NOAA website:

March 6, 2025

Key Points

• Another month of extremely dry conditions plagued the Southwest (Colorado, New Mexico, Arizona, Utah, Nevada), leading to deepening snow deficits across already dry basins. Exceptional snow drought continues to persist with the peak snow water equivalent (SWE) dates past for Arizona and New Mexico.
• Lower-elevation snow drought persisted across southern Alaska due to continued warm and dry conditions, with Anchorage Airport recording its driest February on record. Large areas in southwest Alaska and low elevations in south-central Alaska—which are typically snow covered—were (nearly) snow-free as of March 1.
• Moderate snow drought conditions persisted in the northern and central Cascade Range of Washington due to below-average winter precipitation.
• A recent storm cycle brought welcome moisture back to California and Nevada, improving snow drought conditions, but deficits still remain in the region.
• The Upper San Juan, Upper Rio Grande, and Gunnison River Basins provide substantial snowmelt and runoff to the Upper Colorado River Basin, which drains into Lake Powell. Given low snowpack in these basins, monitoring snow conditions will be critical for future water supply as the basins enter the spring snowmelt season.
• The National Weather Service Climate Prediction Center’s outlooks favor a likely colder and wetter pattern over the next month in the West, which could be favorable for snow accumulation. 

Snow Drought Conditions Summary

This update is based on data available as of Monday, March 3, 2025 at 12:00 a.m. PT. We acknowledge that conditions are evolving.

Current Conditions

Extremely dry conditions across the West in January transitioned to a more active precipitation pattern in February improving the snowpack for much of the West, particularly in the Sierra Nevada, northern Great Basin, and northern Rocky Mountains. In contrast, much of the southern Rocky Mountains, Arizona, and New Mexico saw very little snowfall over the past month. The worst snow drought conditions continue to be in the Southwest, including southern Utah, southwestern Colorado, Arizona, and New Mexico. Snow drought conditions also persist in the northern and central Cascade Range of Washington.

Looking Ahead

The U.S. Bureau of Reclamation weekly water supply report for the Lower Colorado River Basin predicts unregulated inflows into Lake Powell will be 70% of normal in April–July. This is despite 92% of normal snow water equivalent (SWE) in the Upper Colorado Basin, as Colorado river tributary watersheds across central Utah (the San Juan River Basin, the Green Basin, and Gunnison Basin) saw below-normal precipitation and persistent low soil moisture conditions. Spring storms could help boost snowpack, but erasing the deep seasonal deficits across these basins is unlikely. 

Throughout Arizona and New Mexico, above-normal potential for significant wildfires persists through June, according to the National Interagency Fire Center. Wildfire season generally begins earlier and peaks later in these states compared to other areas of the West due to earlier peak SWE and a climatologically dry spring before the monsoon season begins.

Several Western U.S. Stations Have SWE Below the 30th Percentile

---

Rocky Mountain Snow Conditions (Colorado, Idaho, Montana, Utah, Wyoming)

Northern Rockies

Snowpack has generally improved in the northern Rocky Mountains over the past month, with most hydrologic unit code (HUC) 6 basins reporting near- to above-normal snow water equivalent (SWE). However, the Marias and Upper South Saskatchewan Basins in northwestern Montana are still in snow drought, with SWE at 71% and 73% of normal, respectively. Precipitation over most of the Bighorn Mountains in north-central Wyoming was well below normal over the past month, particularly the southern part of the range. Snow drought conditions are present in the central and southern part of the Bighorn Mountains, where SNOTEL stations are reporting 48–92% of normal SWE. 

Central Rockies

Snow drought conditions have persisted and, in some cases, intensified across central and southern Utah and southwestern Colorado. Thirteen SNOTEL stations scattered across south-central and southwest Utah report record-low snow water equivalent (SWE). The Lower Colorado-Lake Mead, Escalante Desert-Sevier Lake, and Upper Colorado-Dirty Devil Basins have 29%, 51%, and 56% of normal SWE, respectively. This is the lowest SWE on record for the Lower Colorado-Lake Mead Basin for this date. The Lower Green Basin, including the south slopes of the Uinta Mountains in northeastern Utah, report 79% of normal SWE.

SNOTEL stations in southwestern Colorado, including stations in the San Juan and Sangre de Cristo mountains, also report snow drought conditions, with most locations below the 20th percentile SWE. Northwestern portions of the Gunnison Basin also have well-below-normal snowpack. The Upper San Juan, Rio Grande Headwaters, and Gunnison Basins are at 56%, 62%, and 82% of normal SWE, respectively. These basins provide substantial snowmelt and runoff to the Upper Colorado River Basin, which drains into Lake Powell. It will be critical to watch snowpack in these basins heading into the spring snowmelt season. February temperatures were 4–6 °F above normal in much of southern Utah and western Colorado, helping drive snow drought across the region.

Low Snow Water Equivalent in Upper San Juan River Basin

---

Arizona and New Mexico Snow Conditions

Snow drought conditions remain severe as much of the region is nearing or has passed the dates at which snow water equivalent (SWE) typically peaks for the year. In Arizona and parts of New Mexico, peak SWE typically occurs around March 1, much earlier than most of the mountains in the West. The trend of persistent above-normal temperatures and lack of snowfall continued in February in the mountains across the region.

All but two SNOTEL stations in Arizona and New Mexico report less than 50% of normal SWE, with no snow at some locations. In Arizona, the Verde Basin, which has a median peak SWE date of March 1, is currently at 8% of median peak SWE, and the Little Colorado Basin, which has a median peak SWE date of March 4, is currently at 17% of median peak SWE. In New Mexico, the Upper Rio Grande and Upper Canadian Basins are at 39% and 28% of normal SWE, respectively. 

Initial surges of spring snowmelt already occurred at some locations in the Upper Canadian Basin, which is several weeks earlier than normal. February temperatures were 4–6 °F above normal across much of the region, which contributed to increased snowmelt at lower elevations.

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor website.

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

Last week brought substantial precipitation (over 1.5 inches) to parts of western Washington, the central and southern Sierra Nevada, southwestern California, portions of the western Mississippi Valley from southern Minnesota into Louisiana and eastern Texas, a swath across the Gulf Coast and South Atlantic States, and the eastern tiers of the mid-Atlantic and Northeast. The highest totals (3 to locally 8 inches) were recorded across northern Florida and adjacent Georgia, and northwesternmost Washington. More than 3 inches also fell on scattered small patches of the Sierra Nevada, in a swath from central Mississippi through western Georgia, and central South Carolina. In contrast, only a few tenths of an inch of precipitation barely dampened most of the Ohio Valley and adjacent Appalachians, and from the central and western Plains to the Pacific Coast, although some of the higher elevations of the central Rockies recorded moderate amounts. Central and southern portions of the Florida Peninsula also recorded a few tenths of an inch at best. Meanwhile, it was an abnormally warm week across the entire northern tier of the country outside far western Washington, from the central Plains eastward through the mid-Atlantic, and across central and southern Texas. Daily maximum temperatures averaged 12 to 15 deg. F above normal for the 7-day period over the central and northern Dakotas and adjacent Minnesota. Somewhat below-normal temperatures were observed from the central Rockies westward to the Pacific Coast and southward to the Mexican Border…

High Plains

Light to moderate precipitation fell on parts of the High Plains Region last week, reducing dryness and drought severity in the middle of the Region across several patches in Wyoming, adjacent northern Colorado, part of north-central Nebraska, and a small area in northwestern Kansas and adjacent areas. Farther south, continued subnormal precipitation induced a broad area of deterioration in central and western Kansas and smaller portions of southern Colorado, but heavier amounts eased conditions in eastern Kansas. The depiction across the Dakotas did not change. During the last 90 days, less than half of normal precipitation was measured across south-central and southwestern Kansas, southeastern Colorado, and a few patches across the Dakotas. At the same time, much of Wyoming, central and northeastern Colorado, and a few swaths from northern Kansas through Nebraska and southwestern South Dakota recorded above-normal amounts. Southwestern Kansas and southeastern Colorado were particularly dry during the last 90 days, receiving less than 25 percent of normal…

West

Areas of moderate precipitation, with isolated heavy amounts, affected the Sierra Nevada, southwestern California, western Washington, and some of the higher elevations across Arizona, Utah, eastern Nevada, and southern Idaho. Most of the large West Region, however, recorded several tenths of an inch or less. Similar to the situation across central and western Texas, dryness and drought may be intensifying at a fairly quick clip across New Mexico, and a large part of the state deteriorated by one category this week. That includes a larger area of D3 along the southern tier of the state, with a small area of D4 introduced in the state’s southwestern interior. Farther west, no intensification was noted this week, but a broad area of D3 and D4 persists across southern California, southern Nevada, and much of Arizona. From central sections of Utah and Nevada southward to the Mexican border and southwestward through southern California, less than half of normal precipitation has fallen since mid-December. The lowest totals (just 2 to 25 percent of normal) extend across the southern Four Corners area. Conditions are considerably better north of Utah and central Nevada, with D3 restricted to a small part of western Montana, and more than half of the area free from dryness and drought.

South

Subnormal precipitation in eastern and southern Tennessee led to some expansion of D0 and D1 there, but most of the central and eastern South Region, from eastern portions of Oklahoma and Texas through Mississippi and western Tennessee, is free of dryness and drought. There are a few isolated areas of dryness across Mississippi, and abnormal dryness is also affecting extreme northwestern Arkansas. But Louisiana is one of only 2 states completely free of dryness and drought on the Drought Monitor. In contrast, some degree of dryness covers the central and western sections of Texas and Oklahoma. Rainfall along the Red River (south) led to some improvements across southern Oklahoma and adjacent Texas, but some degree of dryness remains on the map there. Other parts of Texas and Oklahoma saw little or no precipitation, leading to areas of dryness and drought intensification. The greatest drought intensity (D4, exceptional drought) covers a large part of the Big Bend as well as portions of central Texas, were patches of D4 are surrounded by a large area of D3 (extreme drought). Since mid-December, less than 5 percent of normal precipitation has fallen on the Big Bend while large sections of central, southern, and western Texas reported less than half of normal since mid-January. Generally 20 to 50 percent of normal for the 2-month period was also observed across the Oklahoma Panhandle and adjacent areas. With dry weather, seasonably increasing temperatures, and periods of high winds, conditions could deteriorate rapidly across central and northwestern Texas, reaching into parts of adjacent Oklahoma and New Mexico…

Looking Ahead

The March 13-17 period starts out unusually mild in a large part of the central and eastern U.S. while relatively cool weather stretches from the Rockies to the Pacific Coast. On March 13, temperatures may reach the upper 70’s deg. F as far north as central South Dakota, central Indiana, West Virginia, and North Carolina. Portions of central and southern Texas are expected to top 90 deg. F. It’ll be a little cooler in the mid-Atlantic and Northeast, with highs in the low 60’s deg. F at best, and probably not above 45 deg. F in most of New England. As the period progresses, warm air pushes south and east toward the Atlantic Ocean while a shot of cold air invades the northern Plains. Lows are expected to drop into the teens in parts of the northern Plains that are expected to top 75 deg. F just two days earlier. The cold intrusion looks to be short-lived, with the air mass moderating as it pushes east. On March 17, warmer weather is expected to again build into the Plains. Meanwhile, the western half of the CONUS remains relatively cool. Much of the Sierra Nevada, Cascades, Pacific Northwest Coast, and northern California are anticipating more than 4 inches of precipitation for the 5-day period, with 5 to locally 8 inches possible in northwestern California and adjacent Oregon. Elsewhere from the Rockies westward, fairly widespread light to moderate precipitation is forecast, with heavier totals of 1.5 to locally 4.0 inches falling on some of the higher elevations (particularly in central and northern Idaho) and parts of the central and southern California Coastline. Most lower elevations should expect lesser amounts of several tenths to an inch. Farther east, a swath of heavy rain is anticipated from the lower Ohio Valley southward into portions of the Gulf Coast States. More than 1.5 inches is forecast there, with amounts exceeding 3 inches possible in northeastern Mississippi, northern Alabama, and central Tennessee. Moderate amounts of at least 0.5 inch should fall elsewhere from the Mississippi River to the Atlantic Seaboard, with lesser totals expected over most of Maine, southern Florida, and the western Great Lakes. In the middle of the country, at least a few tenths of an inch of precipitation are forecast for the east-central and northeastern Great Plains and the Upper Mississippi Valley, with amounts approaching of slightly exceeding an inch over most of Minnesota and adjacent portions of South Dakota and Iowa. Dry weather is anticipated across the High Plains and the southern half of the Great Plains, with a few tenths of an inch falling at best.

The Climate Prediction Center’s 6-10 day outlook valid March 18-22, 2025 favors a continuation of below-normal temperatures from the Rockies westward, and warmer than normal weather over most of the central and eastern states. Odds for unusual warmth top 60 percent from the Ohio Valley and mid-Atlantic northward to the Canadian border while there is over a 70 percent chance of unusually cool conditions in the western Great Basin. Hawaii has significantly enhanced odds for above-normal temperatures (over 60 percent), and the dry areas of southern Alaska should also average warmer than normal, although with lower probabilities. Meanwhile, subnormal precipitation continues to be favored across most of Texas and Oklahoma, and there are slightly enhanced chances for drier than normal weather over part of North Dakota and along the South Atlantic Seaboard. The rest of the country should average near- or wetter-than-normal, with the best odds for surplus precipitation over and near the Pacific Northwest. Above-normal precipitation is also favored for the western half of Hawaii and for the dry areas in Alaska.

Click the link to read the article on the NOAA website:

March 10, 2025

Key Points: 

• Season-to-date snowfall was two or more feet below average across portions of the northern Plains and Upper Midwest, and above average downwind of the Great Lakes, in portions of the West and in parts of the central Plains, Gulf Coast, Southeast and Ohio Valley.
• Alaska had its third-warmest winter, while Hawai’i had its second-warmest and fifth-driest winter on record.
• Temperature and precipitation across the contiguous U.S. in February ranked near average.

Other Highlights: 

Temperature

The average temperature of the contiguous U.S. in February was 34.9°F, 1.0°F above average, ranking in the middle third of the 131-year record. Generally, February temperatures were above average across much of the Southwest, Gulf Coast and Southeast and cooler-than-average from the Pacific Northwest to the northern and central Plains. Arizona had its second-warmest February on record.

The Alaska statewide February temperature was 11.8°F, 7.0°F above the long-term average, ranking in the warmest third of the 101-year period of record for the state. The Aleutian region ranked fourth warmest, with much of the state experiencing above-average temperatures. Below-average temperatures were present across the South Panhandle region.

For February, Hawai’i had an average temperature of 64.5°F, 1.4°F above the 1991–2020 average, ranking sixth warmest in the 35-year record.

The meteorological winter (December–February) average temperature for the Lower 48 was 34.1°F, 1.9°F above average, ranking in the warmest third of the record.

The Alaska winter temperature was 13.6°F, 10.0°F above the long-term average, ranking third warmest in the historical record for the state.

Hawai’i had a winter temperature average of 64.9°F, 1.2°F above average, ranking second warmest in the historical record.

Precipitation

February precipitation for the contiguous U.S. was 2.13 inches, which is average for the month. Wetter-than-average conditions were present across much of the Northwest and from the central Mississippi Valley to the East Coast and into parts of the Northeast. Dry conditions were present from parts of the Southwest and Deep South to the Great Lakes and northern Plains, as well as in portions of the Southeast.

Alaska’s average monthly precipitation ranked ninth driest for February, with portions of southwestern and southcentral Alaska having been much drier than average.

Precipitation across Hawai’i in February averaged 1.22 inches, 3.88 inches below average, ranking third driest on record.

The U.S. winter precipitation total was 5.87 inches, 0.92 inch below average, ranking in the driest third of the December–February record.

For the winter season, precipitation ranked in the wettest third of the historical record for Alaska.

Winter precipitation across Hawai’i was 8.52 inches, 8.03 inches below average, ranking fifth driest on record.

Drought

According to the March 4 U.S. Drought Monitor report, about 44.4% of the contiguous U.S. was in drought, up about 2% from the beginning of February. Drought conditions expanded or intensified across the Pacific Northwest, portions of the Southwest, Midwest, southern Plains and Hawai’i. Drought contracted or was reduced in intensity across parts of the Tennessee Valley, Mid-Atlantic, Northern Rockies and parts of the West Coast.

Monthly Outlook

Above-average temperatures are favored to impact the Deep South and Southeast while precipitation is likely to be above average across portions of the Northwest and Great Lakes. Drought is likely to persist or expand across parts of the central and northern Plains, Southwest and Deep South. Visit the Climate Prediction Center’s Official 30-Day Forecasts and U.S. Monthly Drought Outlook website for more details.

Significant wildland fire potential for March is above normal across portions of the Southwest, Deep South and Southeast. For additional information on wildland fire potential, visit the National Interagency Fire Center’s One-Month Wildland Fire Outlook.

---

For more detailed climate information, check out our comprehensive February 2025 U.S. Climate Report scheduled for release on March 13, 2025. For additional information on the statistics provided here, visit the Climate at a Glance and National Maps webpages.

Click the link to read the report on the NRCS website. Here’s an excerpt:

Click the link to read the release on the NRCS website:

March 7, 2025

Northern basins have received more moisture than the south. Early season storms bolstered water year to date precipitation in southern basins but a drier mid-winter has tempered forecasts. Higher latitude basins continue to benefit, with streamflow projections near or above median. 

As of March 1st statewide snow water equivalent (SWE) is at 91 percent of median, relatively consistent from February 1st. Northern water systems continue to trend near or above median, particularly: the South Platte (105%), Laramie and North Platte (102%), the Colorado Headwaters (100%) and combined Yampa-White-Little Snake (96%). The southern half of the state remains below normal with the largest decrease observed in the Arkansas (79%). The Gunnison basin is at 86 percent of median, reflective of its central geographical location on the western slope. While the Gunnison basin follows the broader north south trend, its position further north compared to other southern basins has helped mitigate more extreme deficits. In contrast, the Upper Rio Grande (63%) and the combined San Miguel-Dolores-Animas-San Juan (SMDASJ) (64%) remain drier, with some of the lowest snowpack levels recorded at this point in the season.  

February storms provided some relief, with the Valentines Day storm delivering up to 3.2 inches of SWE in the La Plata Mountains, offering a much needed boost for the SMDASJ basin. “That said, February’s inconsistent storm cycle has not been game changer. While northern basins benefitted the most, that mid-month surge helped slow the freefall in the southern half of the state but wasn’t quite enough to significantly impact overall snowpack conditions,” noted Nagam Gill, NRCS Hydrologist.  

Recent precipitation trends over the past 90 days highlight similar disparities. The Upper Rio Grande and SMDASJ are at just 44 percent of their period of record median precipitation. Northern basins, on the other hand, are sitting in a much better position heading into the peak snowmelt period. The past 30 days show precipitation at 66 percent for the Arkansas basin and 84 percent for the Gunnison basin. Winter precipitation contributes to both snowpack and overall water year precipitation. Snowpack acts as a natural reservoir, storing water at high elevations until melt out, which directly influence streamflow forecasts. While additional precipitation is expected during the summer months, particularly in southern basins during monsoon season the odds of winter driven streamflow fully catching up remain low. 

Statewide reservoir storage sits at 94 percent of median, down slightly from 100 percent this time last year. With spring runoff yet to begin, storage levels are mostly unchanged from last month. Higher capacity reservoirs are generally near historical medians. While McPhee Reservoir is lower at 76 percent of median and at 55 percent capacity most major reservoirs are near to above normal and positioned to potentially further exceed medians during primary runoff. Blue Mesa Reservoir is at 96 percent of median and at 61 percent capacity. Pueblo Reservoir is at 114 percent of median and at 72 percent capacity. Lake Granby is at 101 percent of median and Dillon reservoir is at 91 percent of median. 

Streamflow forecasts for March 1^st closely reflect recent precipitation and snowpack trends. Statewide, the 50% exceedance streamflow remains largely unchanged from last month, currently at 88 percent of median. Of the 86 forecasts points, nearly half are projected to perform at or above 85% of median streamflow. Northern basins, which have benefited from stronger storms, continue to see near median or above median streamflow projections at the 50% exceedance probability. Meanwhile, southern basins, particularly the Upper Rio Grande and combined SMDASJ, remain well below normal. “A critical consideration when reviewing these forecasts is the full range of exceedance probabilities. In regions already experiencing sustained dry conditions, the drier exceedance forecasts (70%, 90% or 95%) may be more likely to materialize if current trends persist. Likewise, if the latter part of the season trends wetter, higher probabilities (30%, 10% or 5%) should be taken into account,” notes Gill. The variability of forecasted volumes means that relying solely on the 50% exceedance forecast may not fully capture the uncertainty inherent in these projections.  

In the Upper Rio Grande, one of the highest output forecast points, Rio Grande near Del Norte, is forecasted at 380 KAF for the primary period April – September (50% exceedance probability). This is below the median of 480 KAF. If drier conditions continue, the 70% exceedance probability is 320 KAF, highlighting the potential if snowpack conditions persist or in the event of earlier melt out dates.  

Following suit in the Arkansas, 50% forecasts have decreased from last month to 92 percent of median. While the 50% probability is slightly below normal there is a potential for streamflow to perform near or below minimum forecasts. Recent discussions suggest that actual streamflow’s in the Arkansas Basin may underperform relative to the NRCS forecast probability suite. NRCS streamflow forecasts are constrained by internal modeling thresholds and do not extend below 95% exceedance probability, meaning that exceptionally dry conditions may not be fully captured within the published forecast range. 

Between March 1-7, storms have been delivering snowfall to much of the state with the southwest corner observing up to 2.5 inches of SWE at Red Mountain Pass. NOAA’s 6-10 day forecast outlook suggests increased chances for precipitation statewide, with the western slope showing slightly higher probabilities and the southwest corner expected to receive higher amounts. Temperature trends indicate cooler than average conditions on the western slope, while the central to eastern regions are projected to remain near normal, with the far eastern plains trending slightly warmer. This pattern would help extend snowpack longevity in the northern and central mountains while also offering a potential boost to moisture starved southern basins. Statewide, peak SWE is typically around April 8, meaning we still have a few weeks left to accumulate more snow.

To put 2025’s snowpack in perspective, the above graph compares March 1 snow water equivalent (SWE) percentages to similar La Niña years, including 1999, 2000, 2006 and 2018. Historically, La niña conditions favor increased snowfall in northern Colorado while the southern basins often experience drier conditions. This trend holds in 2025, with the Upper Rio Grande and SMDASJ tracking close to 2018 levels, a year that observed similar dry patterns. Meanwhile, statewide SWE trends resemble 2000.

For more details see the March 1^st Water Supply Outlook Report.

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor website.

Click the link to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

In the last week, a few swaths of precipitation occurred across the country, including the Sierra Nevada, northwest California and western portions of Washington and Oregon. Some high elevation areas of the West received precipitation as well, mostly outside of the desert Southwest. Some areas of the Upper Midwest and Northeast received a quarter of an inch of precipitation to locally over an inch. At the end of the current drought monitoring period (Tuesday morning), a powerful storm system was emerging into the Great Plains, delivering thunderstorms, high winds and wind-driven snow to parts of the Great Plains and Midwest. While some of this precipitation fell overnight Monday into early Tuesday morning, most of this precipitation will not be accounted for until next week’s U.S. Drought Monitor (USDM) update. Temperatures generally ranged from 5-15 degrees warmer than normal in the Great Plains, with locally warmer readings in the Dakotas and eastern Montana. With some exceptions, temperatures were mostly within 5 degrees of normal across the rest of the Contiguous U.S.

The Southeast U.S. had a mostly dry week, which led to degradations to short- and long-term drought conditions across parts of the Carolinas, Georgia, Alabama and Florida. Mostly dry weather in the lower Midwest and southern Great Plains led to expansion of ongoing abnormal dryness and drought. Drought coverage and severity also increased in the Southwest and in Hawaii, while short-term abnormal dryness developed in south-central Alaska. Improvements to snowpack in parts of Idaho, western Wyoming and southwest Montana led to some improvements to conditions there…

High Plains

Temperatures across most of the High Plains were above normal, with most locations east of the Rocky Mountains finishing the week between 9 and 15 degrees warmer than normal. Some precipitation fell in mountainous areas of Colorado and Wyoming, and snow occurred Monday night into Tuesday morning in parts of the northeast Colorado plains into western and central Nebraska. Most of the High Plains region east of the Rocky Mountains did not see any changes to ongoing drought or abnormal dryness, except for southern Kansas, where abnormal dryness expanded in response to unusually dry weather in the last few months. In western Colorado, moderate and severe drought expanded in coverage due to very low snowpack and growing precipitation deficits. Recent precipitation in west-central Wyoming led to localized improvements to drought conditions there…

West

Precipitation fell across higher elevations of California, northern Idaho and western areas of Oregon and Washington this week. For the most part, drier weather occurred elsewhere. Temperatures were warmer than normal in most of the West, with the warmest conditions of 9-15 degrees above normal occurring in the central and eastern plains of Montana. Recent improvements to snowpack in northeast Nevada, Idaho and southwest Montana led to localized improvements to drought conditions. Meanwhile, to the south across Utah, Arizona and New Mexico, this week’s continued dry weather led to widespread drought degradation as short- and long-term precipitation deficits grew amid soil moisture, streamflow and groundwater deficits. Drought conditions are especially bad from Phoenix westward to far southeast California, where exceptional drought developed this week…

South

Temperatures across the South this week were mostly warmer than normal, with much of Texas and Oklahoma finishing the week 6-10 degrees above normal. A line of thunderstorms associated with this week’s powerful low-pressure systems produced widespread rain of 0.5-1 inches in central and western Oklahoma and central north Texas, though areas east of there did not receive precipitation from this storm system until after the Tuesday morning data cutoff. Scattered drought degradations occurred in the western halves of Texas and Oklahoma, due to increasing precipitation deficits and locally decreasing streamflow and soil moisture. Groundwater and reservoir levels continued to drop in central Texas in the San Antonio area amid very large precipitation deficits, leading to the development of a small area of exceptional drought. Similar conditions in southwest Texas led to the expansion of exceptional drought along the Rio Grande to the El Paso area…

Looking Ahead

Through the evening of Monday, March 10, the National Weather Service Weather Prediction Center is forecasting parts of coastal and high elevation California, along with portions of the high elevation West to receive 0.75 or more inches of precipitation, though this is mostly expected to miss New Mexico, Montana, northern Idaho, Washington and Oregon. A few other corridors of at least a half inch of precipitation are forecast across northern Nebraska, from southeast Oklahoma to South Carolina and the Florida Panhandle, and in New England. Some areas of the Southeast may receive at least 1 inch of rainfall.

Looking ahead to March 11-15, the National Weather Service Climate Prediction Center forecast favors above-normal precipitation in the northern Contiguous U.S. and strongly favors above-normal precipitation in the western, and especially southwestern, U.S. Below-normal precipitation is favored in most of Texas, especially in far southern reaches of the state. Colder-than-normal temperatures are favored across the West, while warmer-than-normal weather is favored across most of the central and eastern Contiguous U.S.

Just for grins here’s a slideshow of early March US Drought Maps for the last several years.

Click the link to read the article on the NOAA website (Tom Di Liberto):

February 27, 2025

…we’ve discussed ad nauseum how complicated El Niño and La Niña are, and how difficult it is to forecast all of the ENSO nuances. Heck, I even wrote a three–part series 75 years ago that evaluated all of our seasonal forecasts (ok, it was 2014-2015 but it still feels that long ago). In a new paper, Azhar Ehsan, friend of the blog and a member of NOAA’s ENSO forecast team, and colleagues analyzed over 20 years’ worth of climate model forecasts of ENSO and found some interesting results.

Why is this paper unique? Well, most seasonal forecasting evaluations focus on model hindcasts, which are forecasts run using past observational data as the start (or initial) condition. For example, if the models are provided the initial conditions on July 1^st, 1983, what forecast would it have made? The nice thing about running on past data is that you already know what occurred and can immediately see how well the forecast did. The downside is that sometimes the model development itself can be influenced by this past data. The purest test for models is how well they do in the future, on data that the model has never ever seen. This type of evaluation on “real-time forecasts” is much rarer, and is exactly what Azhar and his co-authors did.

ENSO Terms and conditions

La Niña and El Niño make up the El Niño/Southern Oscillation, or ENSO. La Niña is characterized by cooler-than-average sea surface temperatures across the central and eastern tropical Pacific Ocean. El Niño is the opposite phase, with warmer-than-average water present across the tropical Pacific Ocean. These changes in sea surface temperature across the Pacific jumble up the atmosphere above which can lead to global impacts on climate patterns. Seems pretty important, right? And unlike most other climate phenomena, the state of ENSO can be forecast months in advance, giving communities time to prepare.

Tell me about that sweet, sweet data

Let me paint you a picture. It’s February 2002. Crossroads starring Britney Spears has just come out, while Ja Rule and Nickelback are burning up the music charts. At Columbia University’s International Research Institute for Climate and Society (IRI), a plucky group of scientists has begun issuing ENSO forecasts. That effort has now become the world’s longest archive of real-time monthly ENSO forecasts from modeling groups across the globe. The list of forecast contributors has continued to grow since 2002, and the tally of the treasure trove of climate model data currently stands at 28 different climate models.

Why so many? No single model forecast is ever going to be exactly correct all the time. To get a sense of the range of potential outcomes, it’s important to not only have a bunch of forecasts using the same climate model due to the chaos of climate but also forecasts from a bunch of different models due to the idiosyncrasies of each individual (we call these combined bunches multi-model ensembles). A well-constructed forecast ensemble won’t tell you precisely what outcome to expect, but it will tell you how much the odds are tilted toward one outcome or the other (i.e., probabilities).

The model forecasts can be split into two types, dynamical and statistical. Dynamical models refer to models which take observational data to simulate earth’s future climate by using equations that represent our best understanding of the laws of physics (e.g., like the computer climate models that make up the North American Multi-Model Ensemble, or NMME, that are frequently featured in this blog). Statistical models, on the other hand, use the historical relationships between ENSO and other climate variables from the observational record and then use these relationships to make predictions for the current situation.

How did the models do?

By analyzing all model forecasts of the seasonal (three-month) Niño-3.4 index from 2002 through 2023, Azhar and his co-authors discovered some interesting patterns. First, it was clear that there was a decent amount of variation in how well both the dynamical and statistical models performed given both when the forecast was made and what season was targeted. From past ENSO blog posts (here, here, and here), we know that the model skill for forecasts made during the spring predictability barrier—a time where models do particularly poorly in forecasting the fall/winter state of ENSO—is not great. But even then, the skill of statistical model forecasts issued just before and during the spring fell off a cliff for target months in early summer and beyond, much more so than dynamical models. However, the skill of statistical and dynamical model forecasts issued in summer and fall were comparable for all times in the future.

Second, there were differences in model performance for predicting El Niño versus predicting La Niña. Overall, models had greater skill in predicting El Niño, compared to La Niña, no matter when the forecast was made, whether it was one month or nine months prior. Dynamical models also outperformed the statistical models in forecasting El Niño at all lead times, and for La Niña for short time horizons. For forecasts of La Niña made five or more seasons out, both statistical and dynamical models performed comparably (and not very well).

Can someone tell me when this El Niño or La Niña turns on?

It’s one thing to predict the strength of an El Niño or La Niña event when its already at its peak and mature, and quite another challenge to correctly predict when an event begins. And one rather interesting finding falls right in line with what we’ve observed so far during the current La Niña.

Azhar and his team found that dynamical models are excellent at predicting the start of El Niño events up to a three-month lead (they are accurate more than ~60% of the time). But for La Niña, yikes. Dynamical models are ok for onset predictions two seasons in the future (40-60% accurate), but after that the accuracy drops to 20% and then to 0 (Footnote 1). Meanwhile, the less I say about statistical models predicting the onset of El Niño and La Niña, the better. Suffice to say, they’re not great.

Remember this analysis did not include 2024. So, the incredibly delayed start to the current La Niña, one that many models missed, was not in this analysis.

Caveats

When it comes to science, usually it’s easier to find the patterns then to determine exactly why those patterns exist. Azhar and his fellow authors shared some potential explanations but solid conclusions will need additional research.

Why is there a difference in skill between dynamical and statistical models? Dynamical models have seen a rapid evolution from 2002 to now. Advancements in computer resources, better observations, and a more complete understanding of our atmosphere and ocean have not just improved existing models but have led to an increase in the number of dynamical models over time. The number of statistical models has remained roughly the same. Though, over the last couple of years, the numbers have been increasing (Footnote 2).

So, why bother including statistical models? For one, statistical models serve as a valuable benchmark to measure more complicated models against. Two, they are much cheaper and thus faster to run. And three, unlike dynamical models where the factors that are driving a certain ENSO forecast may be too mixed together and unclear, statistical models with their simplicity can sometimes allow forecasters to unpack what factors are driving the forecast.

Of course, one major caveat here is that this analysis only looks at a small amount of ENSO events. Nevertheless, some conclusions are clear. Predicting the onset of an El Niño and La Niña event is hard. To which THIS ENSO forecaster (me) says “Tell me about it!”

Footnotes

1) Accuracy here is defined as the ratio of correctly forecasted ENSO onset times to the number of total episodes. A forecast is a “hit” if the forecasted Niño-3.4 index meets or exceeds the threshold for El Niño (+0.5°C) or La Niña events (-0.5°C) at the event onset. A 0% accuracy for a given lead time means that no model correctly forecast the onset of the event at that lead time.

2) There are new types of promising statistical models popping up that incorporate artificial intelligence and machine learning which have been added into the plume. Model evolution is not strictly the domain of dynamical models! Hopefully, additional statistical models can be incorporated into the IRI plume to potentially offer better real-time ENSO forecasts.