Natural hazards · O'Fallon

O'Fallon, IL natural hazards

Most of the natural-hazard damage FEMA expects in O'Fallon comes from inland flooding, and overall the risk is moderate for a U.S. community. Flood insurance has paid 10 claims here since 1979.

FEMA National Risk Index, December 2025 · OpenFEMA claims, aid & declarations

Expected damage

How exposed is O'Fallon?

Moderate

vs. U.S. communities

FEMA expects yearly storm and flood damage to homes and buildings in O'Fallon to be higher than in 59% of U.S. communities, mostly from inland flooding and earthquakes.

Inland flooding32%Earthquakes27%Heat waves13%Cold waves13%Tornadoes10%Everything else6%

By hazard

What O'Fallon faces

Each hazard’s share of the damage FEMA expects here, and how that compares with the rest of the country.

Inland flooding

32% of expected damage

Above average · higher than 56% of U.S. places

Recorded about 2 times a year in the area

Earthquakes

27% of expected damage

Well above average · higher than 84% of U.S. places

Heat waves

13% of expected damage

Well above average · higher than 80% of U.S. places

Recorded about 15 times a year in the area

Cold waves

13% of expected damage

Well below average · higher than 20% of U.S. places

Recorded about once a year in the area

Tornadoes

10% of expected damage

Well above average · higher than 78% of U.S. places

Lower here

HurricanesHailIce stormsWinter weatherWildfireLandslidesStrong windLightningDrought

Not a risk here

Coastal floodingAvalanchesTsunamisVolcanic activity

Flood risk changes street by street. Check a specific address on FEMA’s flood map, and ask about flood insurance before you buy.

Flood insurance claims

Does O'Fallon flood?

Every paid claim on a federal flood insurance policy in O'Fallon, from FEMA’s records.

10paid claims since 1979

$40Kpaid to owners

0homes flooded more than once

19792026

Biggest named events

Mid-spring storms: 3 claims, $7K
Late July Flooding: 1 claim, $7K

of all homes
are insured

No community discount. 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.

Disasters that hit O'Fallon

Federal disasters declared here

None of the disasters declared for St. Clair County shows FEMA aid or repair money reaching O'Fallon itself in FEMA’s records.

Brought FEMA money into O'FallonDeclared for St. Clair County only

St. Clair County has had 17 natural disasters declared since 1953, most often floods and severe storms.

Around O'Fallon

O'Fallon and the towns around it

Very lowLowModerateHighVery high

Shilohmostly inland floodingHigh

Shiloh Valleymostly inland floodingHigh

Caseyvillemostly earthquakesHigh

Lebanonmostly earthquakesHigh

O'Fallonmostly inland floodingModerate

Jarvismostly inland floodingModerate

About these numbers

How to read this page

An average, not a forecastFEMA’s National Risk Index estimates the damage 18 kinds of natural hazards cause in a typical year, from decades of records and models. A quiet decade can follow a bad year.

Compared by rate“Higher than N%” compares yearly damage as a share of what’s here, so a big city isn’t rated riskier just for having more buildings. O'Fallon covers 5 census tracts, combined by population.

Money that reached townFlood claims are matched to O'Fallon’s own flood-insurance community (here, the census tracts inside it); household aid to the registrant’s city; repair grants to the Township of O'Fallon. FEMA’s model follows property values, so a place that recently lost many homes can rate lower than it feels.

FEMA’s expected losses across O'Fallon total about $10.5M a year, counting buildings, people and crops.

Sources: FEMA National Risk Index (December 2025); 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. Census tracts: U.S. Census Bureau.