Published June 6, 2025
Climate Change and Flooding: How Risk Is Shifting Across America
Climate change is fundamentally altering flood risk across the United States. Over the past two decades, FEMA claims data shows a clear pattern: flooding is intensifying in historically flood-prone areas and expanding into regions that previously experienced minimal flood risk. These shifts have major implications for homeowners, insurers, and communities nationwide.
The Science Behind Increased Flooding
According to NOAA climate research, warmer temperatures are increasing the atmosphere's capacity to hold moisture. For every degree Celsius of warming, the atmosphere can hold approximately 7% more water vapor. This translates directly into heavier rainfall events, the type of extreme precipitation that overwhelms drainage systems and causes flooding.
USGS streamflow data confirms these trends. Peak river flows have increased in much of the eastern United States, while the frequency of extreme rainfall events has risen across nearly all regions. The result is more frequent and more severe flooding in counties that may not have historically been considered high-risk.
Where Flood Risk Is Growing Fastest
Analysis of FEMA NFIP claims data reveals distinct regional patterns in how flood risk is shifting:
- Mississippi River Basin, Counties along the Mississippi, Missouri, and Ohio Rivers are experiencing more frequent river flooding as upstream rainfall intensifies
- Southeast, North Carolina, South Carolina, and Georgia are seeing increased hurricane-related flooding and extreme rainfall events
- Northeast, Aging drainage infrastructure combined with heavier rainfall is increasing urban flooding in the mid-Atlantic and New England
- West Coast, Atmospheric rivers are delivering more intense precipitation to California and the Pacific Northwest
- Coastal counties, Sea level rise is compounding storm surge risk along all U.S. coastlines
Inland Counties Face New Risks
One of the most significant shifts is the growth of inland flooding in areas previously considered minimal-risk. Counties that were once considered minimal-risk are now experiencing significant flood events. This is particularly concerning because many inland homeowners do not carry flood insurance, and local infrastructure was not designed for the intensity of rainfall these areas now receive.
Urban flooding is also accelerating as impervious surfaces expand and stormwater systems are overwhelmed by heavier rainfall. Cities that historically managed stormwater effectively are increasingly experiencing backup, ponding, and surface flooding during intense storms.
Impact on Flood Insurance
The shifting risk landscape has major implications for flood insurance. FEMA's Risk Rating 2.0 methodology attempts to incorporate current risk factors, but the program still relies primarily on historical data rather than forward-looking climate projections. This means many properties in areas with rapidly increasing flood risk may be underpriced, while the NFIP faces growing financial exposure.
What Communities Can Do
Communities facing increased flood risk have several adaptation strategies available. Green infrastructure such as rain gardens and permeable pavement can absorb additional rainfall, while updated floodplain management regulations can restrict development in newly vulnerable areas. Some communities are adopting climate-adjusted building standards that go beyond current FEMA requirements.
Check your county's current flood risk score on our rankings page and review our flood mitigation strategies to understand how to protect your property. Visit EPA's green infrastructure resources for guidance on nature-based flood solutions.
Frequently Asked Questions
Climate change increases flood risk through three primary mechanisms: warmer temperatures increase atmospheric moisture capacity (about 7% more moisture per degree Celsius), leading to heavier rainfall events; sea level rise amplifies coastal flooding and storm surge; and shifting weather patterns bring more intense storms to regions historically less flood-prone.
The Midwest, Southeast, and Northeast are experiencing the fastest growth in flood risk. FEMA claims data shows significant increases in counties along the Mississippi River basin, Great Lakes region, and mid-Atlantic coast. Previously low-risk inland areas are also seeing more frequent flooding events.
FEMA flood maps generally do not incorporate forward-looking climate projections. Maps are based on historical data and current conditions, which means they may underestimate future flood risk in areas where climate change is accelerating flooding trends. Some communities are voluntarily adopting climate-adjusted flood standards.