Photo: Robert Lawton · CC BY-SA 2.5More hazard damage per building is expected in O'Fallon than in 63% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, O'Fallon gets a C+ for hazard risk: higher expected damage per building than 63% of U.S. towns, #486 of 768 in Illinois. Most of that expected damage is river and rain flooding (58%), then earthquakes (26%). Flood insurance has paid 12 claims here since 2000.
Graded on FEMA’s expected yearly building damage per dollar of building value (NRI v1.20, December 2025), weighted by where residents live; flood claims are shown, not graded. How hazard risk is graded
What O'Fallon faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
River and rain flooding
Earthquakes
Tornadoes
Hail
Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.
What’s behind O'Fallon’s grade
River and rain flooding is 58% of the building damage FEMA expects in O'Fallon, and O'Fallon’s rate of river and rain flooding damage is higher than 55% of U.S. census tracts. Next is earthquakes at 26% (higher than 83% of U.S. census tracts).
C+ #486 of 768 in Illinois; higher expected damage per building than 63% of U.S. towns (21,298).
O'Fallon’s residents live in 9 census tracts; FEMA’s figures are combined by where they live.
The typical Illinois town has higher expected damage than 54% of U.S. towns; within the state, O'Fallon has more expected damage per building than 63% of Illinois towns.
In dollars, FEMA expects about $14.7M a year in losses across O'Fallon: $8.4M to buildings, the rest to people and crops.
Does O'Fallon flood? Sometimes: 12 flood claims since 2000
Every paid claim on a federal flood insurance policy in O'Fallon, from FEMA’s records: 0.9 per 1,000 homes, fewer than 81% of the 13,809 U.S. towns with a flood insurance record.
- The Mid-spring storms3 claims · $7K
- Hurricane Ike2 claims · $87K
- The Late July Flooding1 claim · $7K
O'Fallon isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: St. Clair County.2 federal disasters brought FEMA money to O'Fallon
Disasters that paid out in O'Fallon itself (aid to households or repair grants to the City of O'Fallon), newest first, with that year’s flood claims.
- 2024Severe Storms, Tornadoes, Straight-line Winds, and Floodng4 households applied for aid$3K aid approved
- 2006Severe Winter Storm$212K to the City of O'Fallon for repairs
St. Clair County has had 16 natural disasters declared by the President since 1953, most often floods, then severe storms. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Old photos of O'Fallon after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the O'Fallon archive →O'Fallon and its neighbors
O'Fallon has the lowest expected damage per building of the 9 graded towns here. Tap a town to see its hazards.
| Town | Hazard risk | Mostly (buildings) | Flood claims |
|---|---|---|---|
| O'Fallon | C+more damage than 63% | river and rain flooding | 12 |
| Fairview Heights | C+more damage than 64% | river and rain flooding | 4 |
| O'Fallon Township | C+more damage than 64% | river and rain flooding | 10 |
| Caseyville Township | Cmore damage than 67% | river and rain flooding | 51 |
| Shiloh | Cmore damage than 74% | river and rain flooding | 2 |
| Shiloh Valley Township | Cmore damage than 74% | river and rain flooding | 1 |
| Swansea | Cmore damage than 75% | river and rain flooding | 17 |
| St. Clair Township | C−more damage than 76% | river and rain flooding | 38 |
| Scott AFB | C−more damage than 80% | river and rain flooding | 1 |
Hazard risk = FEMA’s expected yearly building damage per dollar of building value, vs. the 21,298 U.S. towns we grade; the map is shaded by fifths of the same scale. Flood claims = paid federal flood insurance claims on record.
Get ready for what O'Fallon faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Turn around at flooded roads: a foot of moving water can carry off a car.
- Flood insurance usually takes 30 days to start, so buy it before the forecast.
- Keep papers and medicines up high, in a grab-and-go bag.
- Drop, cover and hold on.
- Strap tall furniture and the water heater to the wall.
- Know how to shut off the gas.
- Pick your spot now: the lowest floor, an inside room, no windows.
- A watch means be ready; a warning means take cover now.
- Keep shoes and a flashlight by the bed.
- Park in a garage or under cover when storms are forecast.
- Stay away from windows while it falls.
- Photograph roof and car damage for your insurer.
- Look up the address on FEMA’s flood map.
- Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
- Get a flood insurance quote early: policies usually start 30 days after you buy.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in O'Fallon
Is O'Fallon at risk for natural disasters?
On FEMA’s National Risk Index, O'Fallon has higher expected damage per building than 63% of U.S. towns: C+ for hazard risk, #486 of 768 in Illinois. Most of the expected damage is river and rain flooding (58%) and earthquakes (26%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does O'Fallon flood?
Flood insurance has paid 12 claims in O'Fallon since 2000, $417K in all, or 0.9 per 1,000 homes, fewer than 81% of U.S. towns with a flood insurance record. 2 properties have flooded more than once. The most claims came from Mid-spring storms (3).
Is O'Fallon in a flood zone?
Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In St. Clair County, 1.0% of all homes carry federal flood insurance.
How much is flood insurance in O'Fallon?
FEMA’s Community Rating System list shows no discount for O'Fallon’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
What was the biggest storm in O'Fallon?
By FEMA money that reached O'Fallon, Severe Winter Storm (2006): $212K to the City of O'Fallon for repairs. By flood claims, Mid-spring storms: 3 paid, $7K.
Is O'Fallon at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (58%), and O'Fallon’s rate for it is higher than 55% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in O'Fallon.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where O'Fallon’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.