Photo: Classiv · CC BY-SA 4.0FEMA puts O'Fallon’s expected hazard damage per building above that of 81% 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 81% of U.S. towns, #204 of 247 in Missouri. Most of that expected damage is river and rain flooding (79%). Flood insurance has paid 45 claims here since 1978.
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 stands out about O'Fallon’s natural hazards
From FEMA’s model and FEMA’s records, below.
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 79% of the building damage FEMA expects in O'Fallon, and O'Fallon’s rate of river and rain flooding damage is higher than 86% of U.S. census tracts. Next is earthquakes at 8% (higher than 78% of U.S. census tracts).
C− #204 of 247 in Missouri; higher expected damage per building than 81% of U.S. towns (21,298).
O'Fallon’s residents live in 25 census tracts; FEMA’s figures are combined by where they live.
The typical Missouri town has higher expected damage than 59% of U.S. towns; within the state, O'Fallon has more expected damage per building than 83% of Missouri towns.
In dollars, FEMA expects about $49.2M a year in losses across O'Fallon: $35.9M to buildings, the rest to people and crops.
Does O'Fallon flood? Sometimes: 45 flood claims since 1978
Every paid claim on a federal flood insurance policy in O'Fallon, from FEMA’s records: 1.2 per 1,000 homes, fewer than 73% of the 13,809 U.S. towns with a flood insurance record.
- The Midwest Flooding8 claims · $498K
- Hurricane Ike4 claims · $117K
- The Late July Flooding2 claims · $117K
O'Fallon is in FEMA’s Community Rating System (class 9) for its flood-proofing work.
Insurance rates: St. Charles County.5 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.
- 2022Severe Storms and Flooding2 households applied for aid$300 aid approved$138K to the City of O'Fallon for repairs2 flood claims paid that year
- 2019Severe Storms, Tornadoes, and Flooding$40K to the City of O'Fallon for repairs1 flood claim paid that year
- 2015Severe Storms, Tornadoes, Straight-line Winds, and Flooding2 households applied for aid$138K to the City of O'Fallon for repairs
- 2008Severe Storms and Flooding$2K to the City of O'Fallon for repairs9 flood claims paid that year
- 2007Severe Winter Storms and Flooding$82K to the City of O'Fallon for repairs
St. Charles County has had 24 natural disasters declared by the President since 1953, most often severe storms, then floods. 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 is 5th of the 8 graded towns here, from least expected damage per building to most. Tap a town to see its hazards.
| Town | Hazard risk | Mostly (buildings) | Flood claims |
|---|---|---|---|
| Lake St. Louis | C+more damage than 58% | river and rain flooding | 5 |
| Wentzville | C+more damage than 62% | river and rain flooding | 4 |
| Weldon Spring | Cmore damage than 70% | river and rain flooding | 1 |
| St. Peters | Cmore damage than 75% | river and rain flooding | 98 |
| O'Fallon | C−more damage than 81% | river and rain flooding | 45 |
| St. Paul | Dmore damage than 87% | river and rain flooding | 1 |
| Dardenne Prairie | Dmore damage than 88% | river and rain flooding | 1 |
| Cottleville | Dmore damage than 91% | river and rain flooding | 27 |
| Josephville | — | 664 residents; we grade 1,000+ | |
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.
- O'Fallon residents get 05% off flood insurance.
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 81% of U.S. towns: C− for hazard risk, #204 of 247 in Missouri. Most of the expected damage is river and rain flooding (79%) and earthquakes (8%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does O'Fallon flood?
Flood insurance has paid 45 claims in O'Fallon since 1978, $1.2M in all, or 1.2 per 1,000 homes, fewer than 73% of U.S. towns with a flood insurance record. 4 properties have flooded more than once. The most claims came from Midwest Flooding (8).
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. Charles County, 35% of homes in mapped flood zones carry federal flood insurance, and 0.8% of all homes do.
How much is flood insurance in O'Fallon?
O'Fallon is in FEMA’s Community Rating System (class 9), which takes 05% off federal flood insurance policies for its flood-proofing work. 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 Storms and Flooding (2022): 2 households applied for aid, $300 approved, and $138K to the City of O'Fallon for repairs. By flood claims, Midwest Flooding: 8 paid, $498K.
Is O'Fallon at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (79%), and O'Fallon’s rate for it is higher than 86% 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.