O'Fallon, Illinois: natural disaster risk
How exposed O'Fallon is to floods, storms and other hazards, from FEMA and NOAA records for St. Clair County.
O'Fallon is a city of 32,262 people in St. Clair County, Illinois. FEMA's National Risk Index rates St. Clair County relatively high for natural hazards overall, higher than most of the US. The costliest hazards there are inland flooding, earthquake and heat wave, with about $175 million in expected losses a year across the county. The weather service has logged 894 storm reports in the county since 1952, including 56 tornadoes and 52 floods. About 1% of homes in the county carry federal flood insurance.
Risk figures are for St. Clair County. FEMA National Risk Index December 2025; NOAA Storm Events; US Census Bureau ACS 2020 to 2024. Updated November 6, 2026.
Top risks in O'Fallon
Full St. Clair County report ›- Check the FEMA flood map for your address, and ask the seller or landlord about past flooding.
- Price a flood policy now. Most new federal policies take 30 days to start.
- Ask whether an older house is bolted to its foundation.
- Consider separate earthquake insurance where risk is high.
- Check that cooling works before summer.
- Know where the nearest cooling center is.
All hazards
| Hazard | Rating | A year |
|---|---|---|
| Inland flooding | $72M | |
| Earthquake | $51M | |
| Heat wave | $15M | |
| Cold wave | $15M | |
| Tornado | $13M | |
| Hail | $5M | |
| Lightning | $2M | |
| Ice storm | $1M | |
| Strong wind | $627K | |
| Winter weather | $333K | |
| Drought | $314K | |
| Landslide | $28K |
Homes in O'Fallon
Older homes and mobile homes usually take more damage in storms, floods and earthquakes. Ask about roof age, flood history and retrofits before you buy or rent.
Strongest tornadoes in St. Clair County
More cities in St. Clair County
Common questions about O'Fallon
Is O'Fallon safe from natural disasters?
O'Fallon is in St. Clair County, which FEMA's National Risk Index rates relatively high overall, higher than most of the US. The biggest hazards are inland flooding, earthquake, heat wave. No place is free of risk, so check the flood map and insurance for any home you consider.
What natural disasters happen in O'Fallon?
By expected yearly losses in St. Clair County, the top hazards are inland flooding (High), earthquake (Moderate), heat wave (High). St. Clair County has been part of 17 federal disaster or emergency declarations for natural events.
Does O'Fallon get tornadoes?
Yes. NOAA records list 56 tornadoes in St. Clair County since 1950; the strongest was an F4 tornado on February 25, 1956. FEMA rates tornado risk in the county high.
Do I need flood insurance in O'Fallon?
Standard home insurance does not cover floods. In St. Clair County, about 1% of homes have federal flood insurance, and FEMA rates inland flooding risk high. Check the FEMA flood map for your address and get a quote even outside a high-risk zone.