Climate Matters•March 26, 2025
Heavier Rainfall Rates in U.S. Cities
KEY CONCEPTS
Climate change is supercharging the water cycle, bringing heavier rainfall extremes and related flood risks across the U.S.
Some 126 U.S. cities (88% of 144 analyzed) have experienced an increase in hourly rainfall intensity since 1970.
Across these 126 locations, hourly rainfall rates are now 15% higher on average than in 1970.
Hourly rainfall intensity has increased in every U.S. region, with the largest average increases among cities in the Upper Midwest, Northern Rockies and Plains, and Ohio Valley.
People, ecosystems, and infrastructure in both wet and dry locations are facing the risks that come with heavier rainfall.
This Climate Matters analysis is based on open-access data from the National Oceanic and Atmospheric Administration (NOAA). See Methodology for details.
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Heavier downpours, higher flood risk
Climate change is bringing heavier rainfall extremes and increased, inequitable flood risk to many parts of the U.S.
For every 1°F of warming, the air can hold 4% more moisture, increasing the chances of heavier downpours that contribute to flash flooding hazards.
According to the Fifth National Climate Assessment, as the climate has warmed over the last six decades, the heaviest rainfall events have become wetter in all major regions of the continental U.S., led by: the Northeast, Midwest, and Southeast.
Heavy downpours bring more rain, faster — causing flash flooding and landslides that can displace families, drown crops, damage infrastructure, and expose people to hazardous debris, contaminants, and water-borne disease.
Learn more: Climate Change and Inland Flooding
The rapid onset of flash floods limits time to get people out of harm’s way. People of color and those living in mobile homes are disproportionately exposed to flooding, especially in rural areas and in the southern U.S.
Children are among the most vulnerable to the physical, mental, and emotional health impacts experienced during and after a flood.
Learn more: Climate Change and Children's Health: Flooding
Higher rainfall intensity in 126 U.S. cities
To understand how rainfall intensity has changed locally, Climate Central calculated long-term trends (1970-2024) in the simple hourly rainfall intensity index for 144 U.S. weather stations.
The simple hourly rainfall intensity index is defined as the total annual rainfall divided by the total hours of rainfall each year (inches per hour). See Methodology for details.
An increase in the simple hourly rainfall intensity index indicates an increase in hourly rainfall rates — in other words, more rain falling per hour. NOAA’s Rain Rate Visualizer videos show various hourly rainfall rates.
Of the 144 locations analyzed, 126 (88%) have experienced an increase in hourly rainfall intensity since 1970.
On average, these 126 locations have experienced a +15% increase in hourly rainfall intensity since 1970.
Increases in hourly rainfall intensity since 1970 were observed across all nine U.S. climate regions analyzed.
Grouping cities by region, the largest average increases in hourly rainfall intensity were observed in the Upper Midwest (+18% on average), Northern Rockies and Plains (+16%); and Ohio Valley (+15%).
Nearly two-thirds of the 144 locations analyzed (94, or 65%) experienced an increase in hourly rainfall intensity of +10% or more.
Rainfall intensity increasing — even in dry places
The locations experiencing the largest increase in hourly rainfall rates span a wide range in mean annual precipitation.
Location | Change in simple hourly rainfall intensity index, 1970-2024 |
|---|---|
Wichita Area, Kan. | +38% |
Reno, Nev. | +37% |
Fairbanks, Alaska | +37% |
El Paso, Texas | +37% |
Sioux Falls, N.D. | +31% |
Bismarck, N.D. | +30% |
North Platte, Neb. | +30% |
Sioux City, Iowa | +29% |
San Angelo, Texas | +29% |
Toledo, Ohio | +28% |
Pittsburgh, Pa. | +28% |
Tucson, Ariz. | +28% |
The increase in hourly heavy rainfall intensity since 1970 has been widespread. The risks posed by short bursts of extreme rainfall are therefore relevant for both wet and dry locations.
And places with high total annual rainfall don’t necessarily experience the largest increases in rainfall intensity.
Warmer future, heavier precipitation extremes
With continued warming, precipitation extremes are likely to increase globally — even in regions with decreasing average precipitation, according to the latest reports from the Intergovernmental Panel on Climate Change.
With 2°C (3.6°F) of global warming, most of the U.S. is projected to see increases in precipitation extremes. The planet has already warmed about 1.2°C (2.1°F).
With 2°C (3.6°F) of global warming, the majority (85% or 2,645) of 3,111 total U.S. counties are likely to experience a 10% or higher increase in precipitation falling on the heaviest 1% of days.
Counties likely to experience at least a 30% increase in extreme precipitation are concentrated in: Tennessee, Alabama, Georgia, Mississippi, Maine, North Carolina, and Kentucky.
Alaska and Hawaii are likely to experience some of the highest levels of extreme precipitation intensification (43% and 30%, respectively) at 2°C (3.6°F) of global warming.
Only by rapidly accelerating efforts to reduce heat-trapping pollution can we ensure that global warming levels remain below 2°C.
A recent study suggests that with very high future levels of heat-trapping pollution (RCP8.5), U.S. flash floods could also intensify — especially in the Southwest. This underscores that risks posed by extreme rainfall affect both wet and dry regions.
These rising rainfall intensity risks are unlikely to be equally shared. A recent study suggests that the burdens of an estimated 26% increase in overall U.S. flood risk by 2050 could disproportionately impact Black communities along the Atlantic and Gulf coasts.
LOCAL STORY ANGLES
Check local flood risk.
Local factors including topography, infrastructure, watershed health, and precipitation trends influence an area’s flood risk.
The Federal Emergency Management Agency’s Flood Map Service Center is the official public source for flood hazard information, searchable by address.
Within NOAA, the National Weather Service’s Interactive Flood Information Map is a hub for information about flood safety and flood hazards in each state. The National Water Prediction Service provides an interactive U.S. map of current flood observations and forecasts. NOAA’s Experimental Flood Hazard Outlook, issued twice daily, summarizes current flood conditions based on the latest river level observations with an assessment of flood risk.
From the U.S. Geological Survey, USGS Flood Information provides maps and resources for current and historical floods across the U.S.
Other sources of local flood risk include First Street's flood model, which provides free general flood risk information for every property in the U.S., searchable by address. Paid plans offer access to detailed property-level information. First Street’s 12th National Risk Assessment, published in February 2025, provides a national overview of trends in real estate value due to climate-related risks.
What can you do to protect against flooding and extreme precipitation?
Individual homeowners can insure their homes, maintain rainwater systems, reduce impervious surfaces on their property, elevate utilities and equipment, and take on low-cost indoor projects recommended by FEMA. Communities can invest in flood management systems, green infrastructure, and watershed restoration.
FIND EXPERTS
Submit a request to SciLine from the American Association for the Advancement of Science or to the Climate Data Concierge from Columbia University. These free services rapidly connect journalists to relevant scientific experts.
Browse maps of climate experts and services at regional NOAA, USDA, and Department of the Interior offices.
Explore databases such as 500 Women Scientists, BIPOC Climate and Energy Justice PhDs, and Diverse Sources to find and amplify diverse expert voices.
Reach out to your State Climate Office or the nearest Land-Grant University to connect with scientists, educators, and extension staff in your local area.
METHODOLOGY
The simple hourly rainfall intensity index was calculated for 144 U.S. weather stations with sufficient data quality over the period of analysis (1970-2024) using hourly rainfall data obtained from two different NOAA sources: the National Centers for Environmental Information (NCEI) Hourly Precipitation Data and the Applied Climate Information System (ACIS), which is developed, maintained, and operated by NOAA’s Regional Climate Centers. NCEI data was used for 1970-2011. ACIS data was used for 2012-2024.
Long-term trends (represented as a percent change in the simple hourly rainfall intensity index) are based on the endpoints (1970 and 2024) of the linear regression trend line.
Summary statistics were reported for 144 of 154 stations due to data completeness issues for 10 stations: Colorado Springs, Colo.; Dallas, Texas; Hazard, Ky.; Kansas City, Mo., Lincoln, Neb.; Orlando, Fla.; Paducah, Ky.; Rapid City, S.D., Shreveport, La.; and Stockton, Calif.
The simple hourly rainfall intensity index is defined as the total annual rainfall divided by the total hours of rainfall each year (inches per hour). This means that the simple hourly rainfall intensity index can show increasing hourly rainfall intensity even if the total amount of annual rainfall is decreasing.
The simple hourly rainfall intensity index is a modification of the simple precipitation intensity index (modified to evaluate per hour rather than per day), one of the Climdex climate extremes indices.
For the detailed methodology, please refer to Climate Central’s 2022 report, Wetter Rainfall Hours in a Warming Climate.