Click the link to read the article on the NOAA website (Amy Butler and Laura Ciasto):

January 16, 2025

We’re briefly popping in because another surge of very cold air looks to drop down from the Arctic over a large region of the central US this weekend and into early next week. We know that the question will be asked: is the cold related to the polar vortex this time? So here we are to provide some answers.

There are two points we want to emphasize:

1. The polar vortex strength, as measured by the speed of the winds around the 60N latitude circle and 10 hPa pressure level, remains stronger than average, and is currently forecast by most models to return to near-record strong wind speeds into early February.

Normally, if the polar vortex is communicating with the surface, which it finally has been in the last couple of days, a strong polar vortex would be associated with persistent warmth over much of Europe, Asia, and the eastern US. (A strong polar vortex is usually associated with a northward shifted jet stream that keeps the coldest air corralled over the pole.) Europe and Asia are indeed anticipating warmer than average conditions next week, but not the US. So something else is going on over the US that is overwhelming the “strong polar vortex” signal.

2. We discussed how we didn’t think the shape or stretching of the polar vortex contributed to the last cold air outbreak, because in the lower stratosphere the vortex was shifted towards Asia and not stretched over North America. However, in this case, the vortex is actually forecast to stretch throughout its entire depth (10-30 miles above the surface) over Canada and the Hudson Bay. So unlike last week, this time the stretched out polar vortex may be associated with the forecasted southward shift of the jet stream, which allows the troposphere’s cold Arctic air to spill into the continental US.

However, we want to reemphasize that “associated with” still does not mean one thing caused another, and in this case, it’s still difficult to understand what is causing what. Additionally, a strong ridge of high pressure has been building up simultaneously near Alaska, which can also help force the jet stream to dive down south over the continental US and bring cold Arctic air with it, independent of the polar vortex.

To sum up: Unlike last time (Jan 5-7), the stretching of the polar vortex is extending through the entire column and is “in-sync” with the extension of the jet. But we don’t know the directionality (what caused what), and other tropospheric factors like the strong Alaskan ridging are definitely big players. And while things are more in-line this time, cold air outbreaks don’t only happen because of the polar vortex.

Click the link to read the article on the Big Pivots website (Allen Best):

January 11, 2025

It was another warm year in Colorado, part of a theme. Russ Schumacher, the state climatologist, reports 2024 was the 4^th warmest on record, 3 degrees warmer than the 20^th century average when temperatures across the state were averaged for the year.

Eight of the 10 warmest years in Colorado’s recorded history have been since 2012.

From his base in Akron, 115 miles northeast of Denver, Joel Schneekloth observed temperatures that fit in with this trend.

“We really had warm days but even warmer nights,” reported Schneekloth, who is a regional water specialist with the Colorado Water Institute. “But we didn’t have a string of 100 degree days like we had in 2012 and 2002. We had 100 just once or twice this year.”

To be clear, it can still get cold in Colorado. This is not quite up to Lake Wobegon standards, where all the children are above average. But all the action has been on the high side of the thermometer — or on the lack of cold.. That was particularly true in December.

The Colorado Climate Center reported 120 new all-time high temperatures along with 25 tied records. Nights, as Schneekloth noted, were also warm. There were 129 records for the high minimum temperature.

On the flip side, it had two all-time cold temperatures.

Notable was the warmth of December. “It was very warm across Colorado, or perhaps more accurately, there was a distinct lack of cold,” Schumacher wrote.

“It really was the lack of any real cold in December that led to the record-breaking temperatures for the month,” he told Big Pivots.

“Highs in the low 70s aren’t especially remarkable in December, but many stations set records for the warmest low temperature for December. For example, at Sedgwick, the lowest temperature in December was 11F – the previous warmest low temperature for December was 9F. This is true at numerous stations in northeastern Colorado. Fort Collins only got down to 15 in December. The previous record  was 12 Akron only got to 10; the previous record was 8.”

At many stations, the second or third warmest low for December was just the previous year (2023), a December with a similar lack of cold.

Precipitation, on the other hand, was above average statewide but not abnormally so, 35th wettest in records across the past 130 years. The story of rain and snow, however, was not uniform. The southern San Luis Valley had its wettest calendar year on record. Lands north of Fort Collins and Greeley, along the Wyoming border, much drier than average.

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

On January 9 and 10, a low pressure system tracked along the Gulf Coast and resulted in widespread precipitation (1 to 2.5 inches, liquid equivalent) from eastern Texas and the Lower Mississippi Valley east to the Florida Panhandle. On the northern extent of this storm, snow blanketed areas from Oklahoma and Arkansas to north Georgia. This precipitation during the second week of January supported drought improvement. However, drought expanded and intensified for the Florida Peninsula, eastern North Carolina, west-central Texas, and the Southwest. During the first two weeks of January, multiple Arctic surface highs shifted south from Canada and temperatures (January 1-13) averaged 4 to 8 degrees F below normal for much of the Great Plains, Middle to Lower Mississippi Valley, and Southeast. A very dry start to the wet season continued to affect southern California with worsening drought conditions, periodic Santa Ana winds, and large wildfires. Enhanced trade winds, typical during a La Niña winter, resulted in improving drought for the windward side of the Hawaiian Islands…

High Plains

The Central High Plains continued to have worsening drought conditions and moderate drought (D1) was expanded across portions of southwestern Nebraska using 60-day SPI, soil moisture below the 10th percentile, and the NDMC short-term blend. Although light precipitation (less than 0.5 inch, liquid equivalent) fell across parts of south-central to southeastern Kansas, this precipitation was too low to justify any improvements. Elsewhere, across the Central to Northern Great Plains, no changes were made as early to mid-January is a dry time of year. D1 was expanded across southwestern Colorado due to low snow water equivalent and 60-day SPI…

West

Severe drought (D2) was expanded to include all of southern California due to the very dry start to the water year to date (WYTD) from October 1, 2024 to January 13, 2025. The D2 coverage coincides with where WYTD precipitation has averaged less than 5 percent of normal. [ed. emphasis mine] A number of locations, including San Diego, are having their driest start to the water year. The D2 covers Los Angeles and Ventura counties which are being affected by periodic Santa Ana winds drying out vegetation and large wildfires. Following the two wet winters, the large reservoirs throughout California are at or above-normal. Based on 90-day SPI, declining soil moisture, and low snow water equivalent, a 1-category degradation was warranted for parts of Arizona and southwestern Utah. A mix of improvements and degradations were made to Idaho and the depiction is generally consistent with the 2024-2025 WYTD precipitation and snowpack. Eastern Washington and much of Oregon are drought-free, but low snowpack supports moderate drought (D1) along the northern Cascades of Washington. A 1-category improvement was justified for a portion of central Montana, based on 90-day SPEI along with snow water equivalent (SWE) above the 75th percentile. As of January 14, SWE was above-normal (period of record: 1991-2020) across the southern Cascades along with eastern Oregon and southwestern Idaho. SWE varies for the Sierra Nevada Mountains, those numbers are beginning to decrease after a drier-than-normal start to January. SWE remained well below-normal across the Four Corners Region…

South

More than 1 to 1.5 inches of precipitation (liquid equivalent) supported improvements for portions of eastern Texas, Arkansas, Louisiana, and Mississippi. The small areas of severe drought (D2) were discontinued in northeastern Mississippi due to: 28-day average streamflows near the 20th percentile, soil moisture recovery, and a consensus of SPIs in D1 at worst. In addition, there is no support for maintaining D2 in the NDMC short- and long-term blends. Precipitation during the first two weeks of January resulted in a slight reduction in extreme drought (D3) across south-central Tennessee. For central Texas which received generous precipitation for this time of year, low 28-day streamflows (below the 20th percentile in D1 and 10th percentile in D2) precluded a larger area for a 1-category improvement. D2 to D3 drought was expanded across the Edwards Plateau of Texas due to 28-day average streamflows below the 10th and 5th percentile, respectively…

Looking Ahead

Another Arctic air outbreak is forecast for the central and eastern U.S. during mid-January as surface high pressure shifts south from Canada. By January 20, subzero minimum temperatures are expected as far south as the Central Great Plains, Middle Mississippi Valley, and Ohio Valley. During January 16-20, little to no precipitation is forecast from the West Coast to the Mississippi Valley with light to moderate precipitation amounts (0.5 to 1 inch) limited to the Southeast. These amounts, however, have been sufficient for rainfall to almost keep up with demand, and the near-normal amounts the past 2 weeks have kept the area out of D0 conditions for the time being, but the situation needs to be closely monitored for signs of increasing dryness impacts. Daily rainfall reports are not available for Mili since the start of January 2025, but 45.59” fell during October-December 2024, above the normal of 36.55” and well above the amount needed to keep up with demand, which is sufficient to keep D0 conditions at bay regardless the rainfall during the past 2 weeks.

The Climate Prediction Center’s 6-10 day outlook (valid January 21-25, 2025) favors below-normal temperatures to persist for much of the contiguous U.S. with the largest below-normal temperature probabilities (exceeding 80 percent) extending from the Mid-Atlantic and Ohio Valley south to the Gulf Coast. Elevated above-normal precipitation probabilities are forecast for the northern Great Plains, Gulf Coast, and portions of the Southeast. Below-normal precipitation is favored for the West, Central Great Plains, Midwest, and New England.

Click the link to access the letter on the AGU website (Guo Yu, Keith S. Jennings, Benjamin J. Hatchett, Anne W. Nolin, Nayoung Hur, Meghan Collins, Anne Heggli, Sonia Tonino, Monica M. Arienzo). Here’s the abstract:

December 23, 2024

Reanalysis products support our understanding of how the precipitation phase influences hydrology across scales. However, a lack of validation data hinders the evaluation of a reanalysis-estimated precipitation phase. In this study, we used a novel dataset from the Mountain Rain or Snow (MRoS) citizen science project to compare 39,680 MRoS observations from January 2020 to July 2023 across the conterminous United States (CONUS) to assess three precipitation phase products. These products included the Global Precipitation Measurement (GPM) mission Integrated Multi-satellitE Retrievals for GPM (IMERG), the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2), and the North American Land Data Assimilation System (NLDAS-2). The overall critical success indices for detecting rainfall (snowfall) for IMERG, MERRA-2, and NLDAS-2 were 0.51 (0.79), 0.49 (0.77), and 0.54 (0.53), respectively. These indices show that IMERG and MERRA-2 reasonably classify snowfall, whereas NLDAS-2 overestimates rainfall. All products performed poorly in detecting subfreezing rainfall and snowfall above 2°C. Therefore, crowdsourced data provides a unique validation source to improve the capabilities of reanalysis products.

Key Points

• The Mountain Rain or Snow citizen science project collected a novel dataset of 39,680 observations of precipitation phases across the US
• The precipitation reanalysis products performed poorly in detecting subfreezing rainfall and snowfall above 2°C
• The crowdsourced data provides a unique validation source to improve the capabilities of reanalysis products

Plain Language Summary

Distinguishing between rain and snow is challenging. This study used a unique crowdsourced dataset from the Mountain Rain or Snow (MRoS) project to allow researchers to better assess the accuracy of reanalysis products used to differentiate rain from snow. We compared the citizen science data with results from three reanalysis products. We found that these reanalysis products all performed poorly in detecting rainfall at subfreezing rainfall or snowfall at warmer air temperatures. Crowdsourced data could help enhance methods used to determine precipitation phases and improve real-time weather forecasts.

Click the link to read the briefing on the Western Water Assessment website:

January 10, 2025 – CO, UT, WY

Despite below average precipitation and warm temperatures during December, snow water equivalent (SWE) is near-normal for about half the region. Below average SWE conditions exist in northern Wyoming, southwestern Colorado and southern Utah, especially in the Escalante and Virgin River Basins where SWE is less than 45% of average. The first seasonal streamflow forecasts suggest near-average runoff in Colorado (90-100%), below average runoff in Utah (80-90%) and much below average runoff in Wyoming (50-80%). Drought conditions were relatively stable during December and cover 39% of the region. Previous forecasts of emerging La Niña conditions did not prove correct; Pacific Ocean temperatures remain near-average (ENSO-neutral) and are expected to remain so through spring. NOAA seasonal forecasts suggest the possibility of above average precipitation in northern Colorado, northern Utah and Wyoming during January and in Wyoming for January-March.

December precipitation in Colorado, Utah and Wyoming was below to much below average except for portions of northern Utah and western Wyoming that saw slightly above average precipitation. Large areas of southern Utah, southern Colorado and central to southeastern Wyoming received less than 50% of December precipitation. In eastern Colorado, many locations received record-low December precipitation. Central Colorado, central Utah and western Wyoming received slightly below average December precipitation.

Regional temperatures were at least 3 degrees above average across all locations. Large areas of Colorado and Utah experienced temperatures that were 6-9 degrees above average. In Wyoming, nearly all locations were 6-9 degrees above average during December and central Wyoming average temperatures were 9-12 degrees above average. Record hot December temperatures were recorded in northern Wyoming.

Snow water equivalent was near-normal (median) for about half of the region on January 1, including most of the Upper Colorado River and Great Basins. Below normal January 1st SWE conditions prevailed in southern Utah, southwestern Colorado and northern Wyoming. The majority of river basins in Colorado and Utah saw a significant decrease in SWE conditions relative to median during December. On a statewide basis, January 1st SWE conditions in Colorado and Utah were near normal (95%) and below normal in Wyoming (83%). Southern Utah is currently experiencing the worst snow drought conditions with the Virgin River Basin at 39% normal and the Escalante River Basin at 43% normal. Six snotel sites in southwestern Utah had no snow on January 1st which set or tied the lowest SWE totals on record. An additional 3 snotel sites in Wyoming had their lowest January 1st SWE conditions on record and an additional 4 sites in Wyoming had the second lowest January 1st SWE value.

The first seasonal streamflow forecasts of the 2025 water year suggest near-average runoff in Colorado river basins and below average runoff in all other regional river basins. In Colorado, seasonal streamflow forecasts suggest between 90-100% of average runoff for all river basins. Runoff in most Utah river basins is forecasted at 80-90% of average except for the Upper Bear (94%), Lower Bear (77%), Escalante (60%) and Virgin (50%). In Wyoming, the seasonal streamflow forecast for the Upper Green, North Platte, Snake and Yellowstone is 70-80% while streamflow forecasts for the Bighorn, Cheyenne, Powder and Tongue River Basins range from 50-60% of average. Except for Blue Mesa Reservoir, below average inflow is forecasted for all other major Upper Colorado River Reservoirs including Lake Powell (81%), Flaming Gorge (69%), McPhee (76%) and Navajo (78%).

Regional drought coverage continued a decreasing trend in December and now covers 39% of the region, compared to 42% of the region in early December. Wyoming remains the epicenter of regional drought with 88% of the state experiencing drought conditions and 26% of the state in extreme drought. The area of extreme drought in the Snake River basin expanded in December. In Colorado, abnormal dry (D0) conditions emerged in the San Juan Mountains and D1 drought conditions were removed near the headwaters of the Arkansas and Colorado Rivers. Drought conditions in Utah were relatively unchanged during December.

Despite previous forecasts indicating the formation of La Niña conditions in the Pacific Ocean, December Pacific Ocean sea-surface temperatures were consistent with ENSO-neutral conditions and there is a 60-80% probability of ENSO-neutral conditions persisting through spring 2025. NOAA monthly forecasts for January suggest an increased probability of above average precipitation for Wyoming, northern Colorado and northern Utah. There is an increased probability of below average precipitation for southern Utah and southwestern Colorado. NOAA forecasts also suggest an increased probability for above average temperatures for the entire region during January. On the three-month timescale, there is an increased probability of above average precipitation for Wyoming and below average precipitation for southern Utah and southern Colorado. The NOAA seasonal forecast for January-March indicates an increased probability of below average temperatures in Wyoming and above average temperatures for southern Utah and southern Colorado.

The New Experimental Winter Forecast is a tool that projects December-March precipitation in the western United States using Pacific and Atlantic Ocean temperatures. The most current forecast uses October – November ocean temperatures and indicates slightly above average winter precipitation for much of the region. The regional pattern of precipitation reflects average Pacific Ocean and warm Atlantic Ocean temperatures. Slightly above average winter precipitation is forecasted for most of the region with the highest precipitation relative to average in southern Utah and the lowest in central Wyoming and eastern Colorado.

December Climate Almanac. Much above average to record hot December temperatures in Wyoming are reflected in the temperature extremes. The highest daily maximum, the minimum maximum and minimum temperatures in the region were observed in Wyoming where temperatures are typically colder than Colorado and Utah.

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

January 10, 2025

2024 was the warmest year on record for the contiguous U.S.; Hurricane Helene was the seventh-most-costly Atlantic hurricane on record

Key Points:

• The average annual temperature of the contiguous U.S. was 55.5°F, 3.5°F above average and the warmest in the 130-year record. 
• Annual precipitation for the contiguous U.S. was 31.58 inches, 1.66 inches above average, ranking in the wettest third of the historical record (1895–2024). 
• The Atlantic basin saw 18 named tropical cyclones and five landfalling hurricanes during 2024—an above-average season. Hurricane Helene was the seventh-most-costly Atlantic hurricane on record.
• The tornado count for 2024 was second highest on record behind 2004 (1,817 tornadoes) with at least 1,735 confirmed tornadoes. When looking at EF-2+ tornadoes, 2024 was the most active year since the historic 2011 season.
• Hurricane Helene’s extensive damage topped the list of 27 separate billion-dollar weather and climate disaster events identified during 2024—the second-highest annual disaster count in the 45-year record. 
• Drought coverage across the contiguous U.S. ranged from a minimum extent of 12 percent on June 11—the smallest contiguous U.S. footprint since early 2020—to a maximum coverage of 54 percent on October 29.

Other Highlights:

Temperature

For the year, temperatures were much-above average across nearly the entire contiguous U.S., with record warm temperatures across parts of the Southwest, Deep South and from the Upper Midwest to the central Appalachians and into the Northeast. Seventeen states (Texas, Oklahoma, Minnesota, Wisconsin, Michigan, Indiana, Ohio, Kentucky, Tennessee, West Virginia, Virginia, Pennsylvania, Maryland, New York, Vermont, New Hampshire and Maine) ranked warmest on record while all but two remaining states across the Lower 48 ranked as one of the warmest five years on record. The U.S. Climate Reference Network (USCRN) also indicated that 2024 was the warmest year on record (2005–24).

The Alaska January–December temperature was 28.9°F, 2.9°F above the long-term average, ranking in the warmest third of the 100-year record for the state. Much of the state had temperatures that were above average for the 12-month period with pockets of near average conditions in the southern and eastern mainland as well as the Panhandle.dle.

Precipitation

Precipitation was above average across portions of the West, central Rockies, Deep South, Upper Midwest, Great Lakes, Southeast and Northeast. Precipitation was below average across much of the Northern Rockies and Plains, parts of the Southwest and portions of the Ohio Valley and Mid-Atlantic region. Louisiana ranked 10th wettest for this 12-month period.

January–December 2024 ranked near the middle of the 100-year record for Alaska, with below-average precipitation observed across parts of the Aleutians, Northwest Gulf, Cook Inlet, Northeast Gulf and much of the Panhandle region. Average- to above-average precipitation occurred throughout much of the rest of the state.

Billion-Dollar Weather and Climate Disasters

The Billion-Dollar Weather and Climate Disasters update is a quantification of the weather and climate disasters that in 2024 led to more than $1 billion in collective damages for each event. During 2024, the U.S. experienced 27 weather and climate disasters each incurring losses that exceeded $1 billion. 2024 ranked second highest for the number of billion-dollar disasters in a calendar year. These disasters included: 17 severe storms, five tropical cyclones, two winter storms, one flooding event, one drought/heat wave and one wildfire event.

The U.S. cost for these disasters in 2024 was $182.7 billion and was fourth highest on record. The total annual cost may rise by several billion as additional costs from identified events are reported over time. There were at least 568 fatalities associated with these events—the eighth-highest number of fatalities on record. The costliest events in 2024 were:

• Hurricane Helene was the costliest event in 2024. It made landfall as a Category 4 storm in the Big Bend region of Florida on September 26, caused catastrophic flash flooding and power outages impacting millions of people from Florida to North Carolina and resulted in at least 219 fatalities. Helene was the deadliest Atlantic hurricane since Maria (2017) and the deadliest to strike the U.S. mainland since Katrina (2005). The current estimated total cost of this disaster was $78.7 billion.
• Category 3 Hurricane Milton made landfall near Tampa, Florida on October 9, caused widespread power outages and flooding and spawned tornadoes across the state. The current estimated total cost of this disaster was $34.3 billion.

Over the last 10 years (2015–24), 190 separate billion-dollar disasters have killed at least 6,300 people and cost approximately $1.4 trillion in damage.

This is also a record 14th consecutive year where the U.S. experienced 10 or more billion-dollar disasters and the fifth consecutive year (2020–24) where 18 or more billion-dollar disasters impacted the U.S.

Since records began in 1980, the U.S. has sustained 403 separate weather and climate disasters where overall damages/costs reached or exceeded $1 billion (based on the CPI adjustment to 2024) per event. The total cost of these 403 events exceeds $2.915 trillion.

Tropical Cyclones

Record- to near-record sea surface temperatures in the Atlantic basin helped fuel the active season that formed 18 named tropical systems during 2024. Eleven of these storms were hurricanes (tied with 1995 for fifth highest on record), including five that intensified to major hurricanes (tied with 1995, 1999, 2008 and 2010 for sixth highest), two of which were Category 5 storms. Five of these 11 hurricanes made landfall in the U.S. (tied with 1893, 2004 and 2005 for fourth highest) and include: Hurricanes Beryl, Debby, Francine, Helene and Milton. Hurricane Helene was the seventh-most-costly Atlantic hurricane on record.

Tornadoes

As the Storm Prediction Center continues to confirm the tornadoes that occurred during 2024, the current count is 1,735, which is the second-highest number of confirmed tornadoes on record (2004 had 1,817) and 142 percent of the 30-year (1991–2020) average of 1,225. Four EF-4 tornadoes were confirmed during 2024 and occurred in: Elkhorn, Nebraska (April 26), Marietta, Oklahoma (April 27), Barnsdall, Oklahoma (May 6) and Greenfield, Iowa (May 21).

Wildfires

The number of wildfires in 2024 was approximately 90 percent of the 20-year (2001–20) average with more than 61,000 wildfires reported over the year. The  total number of acres burned from these wildfires—8.8 million acres—was 26 percent above the 20-year average of nearly seven million acres. The Park Fire, the fourth-largest wildfire in California history, burned nearly 430,000 acres and destroyed over 600 structures.

Alaska saw a below average wildfire year, with approximately 667,000 acres burned during the 2024 fire season—about two-thirds of the state’s seasonal average.

Drought

The year began with approximately 33 percent of the contiguous U.S in drought. Drought coverage shrank as the year progressed and reached the minimum extent for the year at 12 percent on June 11—the smallest contiguous U.S. drought footprint since early 2020. As the summer progressed, hot and dry conditions led to the expansion of drought across the Southeast and Mid-Atlantic as well as across the Plains. By October 29, the extent of drought peaked for the year with more than half of the contiguous U.S. (54 percent) in drought, covering significant portions of the Northwest, Southwest, northern and central Rockies, Plains, Great Lakes, the western and central Gulf Coast states as well as the central Appalachians, Mid-Atlantic and portions of the Northeast.  

Snowfall

The 2023–24 snow season was above average across the southern Cascades, Sierra Nevada, Bitterroots, central and southern Rockies as well as portions of the Adirondack, Green and White mountains in the Northeast. Seasonal snowfall was at least three or more feet below average across parts of the northern Cascades, northern Rockies, the northern Plains as well as much of the Great Lakes and Northeast.

The 2024–25 snowfall season to-date from October 1–December 31, 2024 saw above-average snowfall for locations along the West Coast impacted by early-season atmospheric river events. This includes much of the Cascades, northern Sierra Nevada range, Bitterroots as well as the highest elevations of the central Rockies and adjacent Plains along with locations downwind of the Great Lakes. Snowfall deficits prevailed across the southern Sierra Nevada range and from the northern Rockies to the Upper Midwest and across portions of New England.

Climate Extremes Index

The U.S. Climate Extremes Index (USCEI) for 2024 was more than double the average value, ranking highest in the 115-year record. Extremes in warm maximum and minimum temperatures were both highest on record and the primary contributors to this elevated USCEI value for the nation as well as the regions. In addition, all nine climate regions’ USCEI values ranked in the top-10 percent of extremes. Annual extremes across the Southeast and South regions were highest and second highest on record, respectively, and can also be attributed to extremes in one-day precipitation. Near-record extremes across the Upper Midwest were also due to elevated extremes in one-day precipitation and ranked third highest. Across the Northeast, wet Palmer Drought Severity Index (PDSI) values and the number of days with precipitation were elevated and across the Northwest, extremes in one-day precipitation and days with precipitation contributed to the much-above average USCEI values for 2024. The USCEI is an index that tracks extremes (falling in the upper or lower 10 percent of the record) in temperature, precipitation, drought and landfalling tropical cyclones across the contiguous U.S.

This annual summary from NOAA National Centers for Environmental Information is part of the suite of climate services NOAA provides to government, business, academia and the public to support informed decision-making. For more detailed climate information, check out our comprehensive Annual 2024 U.S. Climate Report. 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:

January snowpack conditions reveal contrasting trends across Colorado, with early season storms boosting accumulation in the southern basins before tapering off, while northern basins were favored through December and received a notable boost from early January storms.

---

Denver, CO – January 10th, 2025 – Statewide snow water equivalent (SWE) is 108 percent of the 1991-2020 median as of January 7^th. For context, SWE at this time last year was 76 percent of median, reflecting very different early season conditions. A notable storm during the first week of January 2025 delivered higher amounts of snowfall to northern basins. SNOTEL site Tower recorded impressive gains, with a SWE increase of 6.3 inches. Statewide, streamflow forecasts at the 50 percent exceedance probability are 99 percent of median. Water year to date precipitation as of January 1st is above normal at 104 percent of median and jumped to 108 percent of median on January 7^th.  

Early season storms brought snowfall to southern basins, leading to above average accumulation by mid-November. The combined San Miguel-Dolores-Animas-San Juan (SMDASJ) reached 171 percent of median by mid-November before tapering to 87 percent of median following several dry weeks. Despite recent dry weeks, late season monsoonal precipitation improved soil moisture levels, enhancing the basin’s overall runoff efficiency. At the start of the 2025 water year, soil moisture levels in southern basins ranged from 90 percent to 130 percent of median.  The Upper Rio Grande also had a strong early season start and peaked at 203 percent of median snowpack in November and is now at 82 percent of median. The Arkansas basin is currently at 103 percent of median, maintaining above normal snowpack levels through December.  

Between October and early November, statewide precipitation reached 110 percent of median, with southern basins benefitting most from consistent storms. During this period, basins like the SMDASJ and Upper Rio Grande were well above normal at 186 and 168 percent of median, respectively. In contrast, the South Platte and Laramie-North Platte basins received 55 and 65 percent of October median precipitation, respectively. November precipitation continued a varied trend highlighting a boost in eastern basins such as the South Platte at 167 percent of median and the Arkansas at 209 percent of median. Although December conditions remained dry for most basins, with statewide 30-day precipitation at 74 percent of median on January 1st, northern regions received relatively higher precipitation. For this 30-day period on January 1st the South Platte is at 100 percent of median, the Laramie-North Platte at 103 percent and the Yampa-White-Little Snake at 95 percent of median.  

Streamflow forecasts range from 82 percent in the Laramie-North Platte to 107 percent in the Arkansas basin at the 50 percent exceedance probability. While many forecasts remain near or slightly below median, the range of exceedance probabilities illustrates varying levels of uncertainty across basins. “January forecasts also have the widest range of exceedance probabilities, given that there is still much snow accumulation season to come, so as always we encourage you to consider the full suite of exceedance probabilities in addition to the 50%,” noted Karl Wetlaufer, NRCS forecast hydrologist, emphasizing the importance of monitoring future conditions. Another good reminder to consider the full suite of exceedance forecasts rather than focusing solely on median values when interpreting potential outcomes. 

As of January 2025, reservoir storage across Colorado stands at 93 percent of median statewide, a slight decline from the same time last year but not drastically lower. Reservoir levels reflect carryover from last season, with many basins showing relatively stable conditions. The Arkansas and Upper Rio Grande basins, report 114 and 124 percent of median storage, respectively, highlighting increased storage compared to the previous year. Conversely, the Gunnison and SMDASJ basins report below median storage. “Reservoir levels at this time of year are more of a baseline rather than a predictor, as they depend on upcoming snowmelt contributions during spring runoff,” notes Nagam Gill, NRCS hydrologist. 

Click the link to read the article on the NOAA website (Emily Becker):

January 9, 2025

La Niña conditions emerged in the tropical Pacific in December. There’s a 59% chance La Niña will persist through February–April, followed by a 60% chance of neutral conditions in March–May. Read on for the recent observations that led us to declare the (long-awaited) onset of La Niña and lots of details for current and potential upcoming conditions.

Just the facts, ma’am

A quick briefing, if you’re just joining us—La Niña is one phase of the El Niño/Southern Oscillation (ENSO), a pattern of sea surface temperature and atmospheric changes in the tropical Pacific Ocean. La Niña’s signature is cooler-than-average surface water in the east-central Equatorial Pacific, while its counterpart, El Niño, features warmer-than-average surface water. The atmospheric circulation over the tropical Pacific, called the Walker circulation, exhibits characteristic changes during La Niña and El Niño, so we call ENSO a “coupled” ocean-atmosphere system. ENSO is a seasonal phenomenon, meaning it lasts for several months in a row. The atmospheric changes of ENSO are communicated all around the world, changing temperature and rain/snow patterns in known ways.

Time to get down to brass tacks

Ok! We’ve been expecting La Niña to show up since last spring. While she’s dragged her heels, all the pieces came together this past month.

The tropical Pacific sea surface temperature loitered in ENSO-neutral since April 2024, with our primary ENSO monitoring index, the Niño-3.4 index, within 0.5 °C of the long-term average. In December, however, the Niño-3.4 index was -0.6 °C, according to the ERSSTv5, our most reliable long-term sea surface temperature dataset.

With the Niño-3.4 Index exceeding the La Niña threshold of -0.5 °C, we can move on to the second box on our flowchart—do we think the Niño-3.4 index is going to stay in La Niña territory for the next several seasons? (“Seasons” here means any 3-month-average period.) The consensus among our computer climate models is yes. Also, there is a substantial amount of cooler-than-average water under the surface of the tropical Pacific, which will provide a source for the surface over the next few months.  

So, we’re on to the third box, which has actually been checked for a while now (more on that later). The atmosphere has been looking La Niña-ish for months, with stronger-than-average trade winds, more clouds and rain over Indonesia, and drier conditions over the central Pacific—all hallmarks of an amped-up Walker circulation. In December, the Equatorial Southern Oscillation Index (EQSOI), which measures the difference in surface pressure between the western and eastern Pacific, was 1.5 (positive values indicate a stronger Walker circulation). In fact, this is the 5^th-strongest December EQSOI in the historical record. Drumroll… La Niña conditions have developed.

Break it down for me

There are a lot of different tidbits I want to tell you about this month, so let’s go Q&A-style.

How long will La Niña last?

There’s a reason our flowchart says “the next several seasons” instead of providing a specific number: we can make predictions, but it’s impossible to know ahead of time exactly how long La Niña conditions will last. To be categorized as a La Niña event in our historical record, the three-month-average Niño-3.4 Index (the Oceanic Niño Index) needs to stay at least 0.5 °C below average for at least five consecutive, overlapping seasons. Current odds are 60% that the March–May Oceanic Niño Index will be neutral, which would make this event last fewer than five. That’s not to say it’s impossible for this La Niña to last longer, of course—nature is always full of surprises!  There is a ~40% chance for La Niña to persist into March-May 2025.

How strong will La Niña be?

It’s very likely this La Niña will be weak, with the Niño-3.4 index unlikely to reach -1.0 °C for a season. This is based on computer model guidance and how late in the year La Niña conditions emerged. ENSO events peak in the northern Hemisphere winter, and there’s just not a lot of time for La Niña to strengthen.

Can La Niña still affect our winter climate?

Sure can, although a weak La Niña tends to have a weaker influence over temperature and precipitation patterns.

Why was La Niña so slow to develop?

The short answer to this is “we don’t yet know.” The emergence of La Niña-like atmospheric conditions before substantial tropical Pacific Ocean surface cooling was unusual, though. The global oceans have been running much, much warmer than average for more than a year, which might have had a hand in La Niña’s delay. When we calculate the Niño-3.4 index but account for the temperature of the tropical oceans (the “Relative Niño-3.4 index”) we get an index that’s been in La Niña territory for months. Only this past year or so has the difference between the traditional and relative Niño-3.4 indexes been so large, and we’re still researching this new measurement and all the implications for ENSO development and impacts in a warmer world.

Has La Niña had any impact on temperature and rain patterns yet?

La Niña affects global climate primarily through atmospheric changes, and since the tropical atmosphere has been looking like La Niña for a while, this is a reasonable question! The global climate is incredibly complicated, and even a big factor like ENSO is only one player. Other climate patterns, climate change trends, and random variability can have a strong influence on overall seasonal patterns. That said, it’s interesting that the October–December 2024 temperature and rain/snow patterns over the U.S. resemble the expected patterns from previous La Niña events. See the October–December La Nina temperature and rain/snow maps, and here’s the general page if you would like to poke around.

Temperature has a strong influence from climate trends, and the October–December 2024 temperature pattern over the U.S. is clearly dominated by more warmth.

You’re running out of column inches. Any last tidbits?

Thanks for asking! Speaking of La Niña impacts, you might recall there’s a link between La Niña and active Atlantic hurricane seasons. In brief, La Niña reduces vertical wind shear—the difference between near-surface winds and upper-level winds—and makes it easier for hurricanes to grow. Interestingly, the August–October 2024 wind shear in the Atlantic Main Development Region (an area of the Atlantic where hurricanes tend to develop) was the weakest since 1950 (h/t NOAA’s Matt Rosencrans). We can’t say how much of it was related to La Niña, but given the relative Niño-3.4 index has been in La Niña territory for a while now, it’s an interesting situation that bears more research.

The bottom line

As this unusual La Niña progresses, we’ll be here to keep you updated on all things ENSO!

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

On January 4 and 5, a low pressure system developed across the Central Great Plains and then tracked eastward to the Mid-Atlantic. Along its track, widespread precipitation (1 to 2 inches, liquid equivalent) was observed throughout eastern Kansas, Missouri, the Ohio and Tennessee Valleys, Central Appalachians, and Mid-Atlantic. Total snowfall amounts were near or more than a foot in portions of these areas. This winter storm also resulted in freezing rain for the Ohio Valley and parts of Virginia and West Virginia. Drought improvements were generally made to portions of the central and eastern U.S. where precipitation amounts exceeded 1 or 1.5 inches, liquid equivalent. Drought coverage and intensity continued its decline for the Upper Ohio Valley and New England. After the winter storm exited the East Coast, an arctic air outbreak overspread the eastern two-thirds of the lower 48 states. A favorable start to the wet season coupled with above-normal snowpack supported a decrease in drought coverage across the Pacific Northwest. Conversely, drought worsened for southern California and the Southwest. Alaska and Puerto Rico remained drought-free, while short-term drought intensified across Hawaii…

High Plains

Based on 30 to 60-day SPI along with a lack of early season snowpack, a 1-category degradation was made to southwestern Colorado. Farther to the north across northwestern Colorado, improving snowpack resulted in a minor reduction in abnormal dryness (D0). Southwestern Nebraska has received little to no precipitation during the past 7 weeks, prompting an expansion of D0. In addition, above-normal temperatures during the late fall and into the early winter exacerbated increasing short-term dryness. Heavy precipitation (more than 1 inch, liquid equivalent) for this time of year resulted in a 1-category improvement to northeastern Kansas. No changes were made to the Dakotas and early January is one of the driest times of the year…

West

A dry start to the winter and using 90-day SPI and soil moisture, moderate drought (D1) was expanded across southern California. The NDMC short-term blend, 90-day SPI, and many 28-day average streamflows below the 10th percentile supported the addition of severe drought (D2) to portions of southern California. The Santa Ana winds during early January are likely to exacerbate the worsening drought conditions. Consistent with the NDMC short-term blend along with 30 to 120-day SPI, D2 was expanded for portions of southeastern Arizona and southwestern New Mexico. Based on water year to date (WYTD: October 1, 2024 to January 6, 2025) precipitation averaging above normal and snow water equivalent (SWE) above the 80th percentile, a 1-category improvement was made to southwestern Idaho, eastern to central Oregon, eastern Washington and a small part of northwestern Montana. This 1-category improvement is also supported by NDMC drought blends and SPIs at various time scales. As of January 7, SWE was above-normal (period of record: 1991-2020) across the southern Cascades along with eastern Oregon and southwestern Idaho. SWE was highly variable for the Sierra Nevada Mountains and below-normal across the Four Corners Region…

South

Based on 30 to 120-day SPI, 28-day streamflow, and soil moisture, a 1-category degradation was made to portions of the Edwards Plateau of Texas. SPIs at various time scales and soil moisture supported a 1-category degradation as well for parts of the Rio Grande Valley. Heavy rainfall during late December supported additional improvements across southeastern Texas. Recent rainfall (1 to 2 inches) prompted a 1-category improvement to parts of Mississippi and Tennessee. Despite the recent rainfall, 28-day average streamflow and 90-day SPI support a continuation of D1-D3 intensity for the Tennessee Valley. Although precipitation was lighter this past week, the lack of any support among the indicators for D0 and D1 led to improvements to much of Arkansas…

Looking Ahead

A low pressure system is forecast to develop along the western Gulf Coast by January 10 with a rapid eastward track offshore of the Mid-Atlantic one day later. A large area of 1 to 2.5 inches of rainfall is expected for eastern Texas and the Lower Mississippi Valley, while accumulating snow occurs from the southern Plains east to the Tennessee Valley and Southern Appalachians. High elevation snow is forecast to shift east from the Cascades to the northern Rockies on January 10 and 11. Farther south across California, dry weather is likely to persist through mid-January. On January 13, another Arctic high is forecast to shift south from Canada to the Great Plains.

The Climate Prediction Center’s 6-10 day outlook (valid January 14-18, 2025) favors below-normal temperatures for a majority of the lower 48 states. The largest below-normal temperature probabilities (exceeding 80 percent) are forecast for the Southeast. An increased chance of above-normal temperatures is limited to the Dakotas and Minnesota. Below-normal precipitation is most likely across the Pacific Northwest, Great Basin, and much of California. Elevated above-normal precipitation probabilities are forecast for the Southwest, Texas, and High Plains, while below-normal precipitation is slightly favored along the East Coast.

Just for grins here’s a slideshow of early January US Drought Monitor maps for the past few years.

Albert Van Dijk, Australian National University

Last year, Earth experienced its hottest year on record − for the fourth year in a row. Rising temperatures are changing the way water moves around our planet, wreaking havoc on the water cycle.

The 2024 Global Water Monitor Report released today shows how these changes are driving extreme events around the world. Our international team of researchers used data from thousands of ground stations and satellites to analyse real-time information on weather and water underground, in rivers and in water bodies.

We found rainfall records are being broken with increasing regularity. For example, record-high monthly rainfall totals were achieved 27% more frequently in 2024 than at the start of this century. Record-lows were 38% more frequent.

Water-related disasters caused more than 8,700 deaths and displaced 40 million people in 2024, with associated economic losses topping US$550 billion (A$885 billion). The number and scale of extreme weather events will continue to grow, as we continue pump greenhouse gases into an already overheated atmosphere. The right time to act on climate change was about 40 years ago, but it’s not too late to make a big difference to our future.

Humanity in hot water

Warmer air can hold more moisture; that’s how your clothes dryer works. The paradoxical consequence is that this makes both droughts and floods worse.

When it doesn’t rain, the warmer and drier air dries everything out faster, deepening droughts. When it rains, the fact the atmosphere holds more moisture means that it can rain heavier and for longer, leading to more floods.

---