Wetter Rainfall Hours in a Warming Climate

Climate Central's analysis of 150 U.S. weather stations shows that 90% experienced an increase in hourly rainfall intensity between 1970 and 2021, with an overall average increase of 13%. This trend is linked to the Clausius-Clapeyron equation, where warmer air holds more moisture, increasing the frequency and intensity of heavy downpours. Such extremes contribute significantly to flash flood risks, accounting for approximately one-third of U.S. flood damages ($73 billion) from 1988 to 2017. Future projections suggest that U.S. flash floods could intensify by 8% by 2100 under high-emission scenarios, with the Southwest and central U.S. identified as high-risk areas.

• Between 1988 and 2017, increases in rainfall were responsible for approximately one-third of all flood damages in the United States, totaling about $73 billion of the $210 billion in total damages.
• The relationship between air temperature and water vapor is governed by the Clausius-Clapeyron equation, which dictates that for every 1 °F of warming, the air can hold an additional 4% of moisture. Since 1970, the U.S. has warmed by 2.6 °F, allowing the atmosphere to hold roughly 10% more moisture.
• From 1958 to 2016, the heaviest 1% of rainfall events became significantly wetter in the Northeast (55%) and Midwest (42%), while other regions of Alaska and the contiguous U.S. saw increases between 9% and 29%.
• An analysis of 150 U.S. weather stations from 1970 to 2021 found that 90% of stations saw an increase in hourly rainfall intensity. The average increase across these stations was 13%, with 63% of stations experiencing an increase of 10% or more.
• The highest increases in hourly rainfall intensity were observed in Fairbanks, Alaska (49%) and El Paso, Texas (40%). Most of the top 10 locations with the greatest increases have mean annual precipitation below the national average of 31.3 inches.
• Under a high-emissions scenario, U.S. flash floods could intensify by approximately 8% by the year 2100, with the Southwest projected to see the greatest increase and the central U.S. potentially becoming a new hotspot.
• Future flood risks are expected to be distributed inequitably; while poorer, predominantly white populations currently face the brunt of risk, future risks are projected to disproportionately affect Black communities along the Gulf and Atlantic coasts.

APA

Climate Central (2022). Wetter Rainfall Hours in a Warming Climate. https://ccimgs-2022.s3.amazonaws.com/2022HourlyRainfall/2022HourlyRainfall_Report.pdf

Chicago

Climate Central. Wetter Rainfall Hours in a Warming Climate. 2022. https://ccimgs-2022.s3.amazonaws.com/2022HourlyRainfall/2022HourlyRainfall_Report.pdf.

Wikipedia

{{cite report |author=Climate Central |title=Wetter Rainfall Hours in a Warming Climate |date=April 2022 |url=https://ccimgs-2022.s3.amazonaws.com/2022HourlyRainfall/2022HourlyRainfall_Report.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{climatecentral2022wetter, author = {{Climate Central}}, title = {{Wetter Rainfall Hours in a Warming Climate}}, institution = {Climate Central}, year = {2022}, month = apr, url = {https://ccimgs-2022.s3.amazonaws.com/2022HourlyRainfall/2022HourlyRainfall_Report.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }