Williamson County, Illinois

Williamson County, Illinois has a moderate overall risk from natural hazards in FEMA's National Risk Index. Its risk score is higher than 86% of US counties. It ranks 17th of 102 counties in Illinois. The costliest hazards here are earthquakes, inland flooding and strong wind. FEMA estimates about $53 million a year in expected losses, or roughly $783 per resident. Since 1982 it has been included in 7 federal disaster or emergency declarations for natural events (5 major disasters). The most recent was in June 2011 (severe storms and flooding). Fewer than 1 in 100 homes here carry federal flood insurance (141 policies). Since 1978, federal flood insurance has paid about $2.1 million on 239 claims here.

FEMA National Risk Index December 2025; OpenFEMA declarations to Nov 6, 2026; NFIP records. Updated November 6, 2026.

Scores are percentiles: a score of 90 means higher risk than about 90% of US counties for that hazard. Hazards FEMA does not rate here are left out. Social vulnerability is relatively moderate and community resilience is relatively high in FEMA's measures.

The National Weather Service has logged 370 storm reports in Williamson County since 1957, with 11 deaths and 237 injuries and about $496 million in reported damage. The strongest on record here was an F4 tornado on May 29, 1982.

Source: NOAA Storm Events Database, county-based reports through Apr 27, 2026. Tornado records start in 1950, hail and wind in 1955, and floods and other storm types in 1996, so older decades undercount. Damage is in dollars of the year it happened and is often an estimate. Winter storms, heat and hurricanes are logged by forecast zone, not county, so they are not counted here.

National Flood Insurance Program (NFIP) records only; private flood policies are not included. Home counts as of Aug 3, 2026. Since 2021 NFIP prices each home separately under Risk Rating 2.0, so your price depends on the building, not the county. Ask an agent for a quote.

Older homes and mobile homes usually suffer more damage in storms, floods and earthquakes, and can cost more to insure. If you are buying, ask about roof age, foundation bolting and any retrofits. Source: US Census Bureau, American Community Survey 2020 to 2024 5-year estimates; 32,084 housing units.

Sources: FEMA National Risk Index (December 2025), OpenFEMA Disaster Declarations Summaries, and NFIP policy and claims data. Hazard Compass is independent and not affiliated with FEMA. These figures describe the whole county, not a single property, and are not insurance or safety advice. Report a problem.