From Climate Central:
Climate change intersects with hurricanes by increasing storm rainfall, intensity, and surge.
A warming atmosphere causes more evaporation, meaning more water is available for precipitation. For every 1°F increase in temperature, the atmosphere can hold around 4 percent more water vapor, which leads to heavier rain and increases the risk of flooding of rivers and streams. We saw the impact of extreme rainfall during Harvey. Though no research has yet been done to attribute the staggering rainfall totals from this storm to climate change, the downpours are very much in line with heavy precipitation trends.