Williamson County, Illinois: Natural Disaster Risk and History
Williamson County, Illinois has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 85.8 out of 100, higher than about 85% of US counties, with strong winds, earthquakes and heat waves scoring highest of its 18 hazards and $53 million a year in expected losses.
OpenFEMA lists 7 federal disaster declarations that included Williamson County since 1982, not counting 2 for COVID-19; the latest is DR-1991-IL (Severe Storms and Flooding, declared 7 June 2011). NOAA's Storm Prediction Center recorded 23 tornadoes touching Williamson County from 1950 to 2025.
Live weather alerts for Illinois All official warnings Latest FEMA declarations
Population 67,101 Buildings worth $16 billion Area 449 sq mi Risk rank in Illinois 17 of 102 FIPS 17199
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Strong wind | Very High | 99.1 | $7.5 million | about 4.1 a year | 156 |
| Earthquake | Relatively Moderate | 96.3 | $20 million | about once every 120 years | — |
| Heat wave | Relatively Moderate | 90.7 | $2.9 million | about 1 a year | 144 |
| Winter weather | Relatively High | 89.8 | $364,090 | about 7.6 a year | 145 |
| Cold wave | Relatively Moderate | 86.9 | $5.0 million | about 1.2 a year | 22 |
| Ice storm | Relatively Moderate | 81.9 | $428,462 | about once every 1.3 years | 54 |
| Tornado | Relatively Moderate | 80.3 | $3.6 million | about once every 2.7 years | 16 |
| Landslide | Relatively Low | 79.3 | $13,054 | about once every 2.1 years | — |
| Hail | Relatively Moderate | 78.3 | $720,700 | about 3.3 a year | 124 |
| Inland flooding | Relatively Low | 69.9 | $12 million | about 2 a year | 57 |
| Lightning | Relatively Moderate | 67.7 | $409,490 | about 53 a year | 220,056 strikes |
| Drought | Relatively Low | 54.2 | $178,366 | about 3.2 a year | 119 |
| Hurricane | Very Low | 44.5 | $39,083 | about once every 45 years | 6 |
| Wildfire | Very Low | 14.2 | $4,288 | rarer than once in 1,000 years | — |
| Avalanche | Not Applicable | — | — | — | — |
| Coastal flooding | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
| Volcanic activity | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 7
Most common: Severe Storm 3, Tornado 2, Hurricane 1, Snowstorm 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1980s | 1 | Tornado |
| 1990s | 1 | Severe Storm |
| 2000s | 4 | Severe Storm, Hurricane, Snowstorm, Tornado |
| 2010s | 1 | Severe Storm |
The last 7
Widest declarations that included Williamson County
- Hurricane Katrina Evacuation (2005, EM-3230-IL): 102 Illinois counties designated.
- Severe Storms, Tornadoes and Flooding (2002, DR-1416-IL): 68 Illinois counties designated.
- Severe Storms and Flooding (1996, DR-1112-IL): 28 Illinois counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Illinois also had 2 statewide declarations with no county list.
Tornado record since 1950 23
| Tornadoes touching the county | 23 |
|---|---|
| Strongest-rated | (E)F4 ×3 |
| Peak month | April (9) |
| Deadliest | 18 Dec 1957, F4, 28.3 mi path, 11 killed, 200 injured |
| Longest path | 18 Dec 1957, F4, 28.3 mi path, 11 killed, 200 injured |
| Most recent | 16 May 2025, EF4, 16.3 mi path, 0 killed, 7 injured |
| Deaths / injuries on those paths | 21 / 407 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 2 | 12 | 5 | 1 | 3 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 1 | 1 | 1 | 1 | 2 | 2 | 9 | 6 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Williamson County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Williamson County (this page) | — | Relatively Moderate | 85.8 | Strong wind |
| Franklin County | 29 km | Relatively Low | 80.9 | Earthquake |
| Johnson County | 30 km | Relatively Low | 51.1 | Earthquake |
| Saline County | 34 km | Relatively Low | 70.1 | Earthquake |
| Jackson County | 40 km | Relatively Moderate | 87.1 | Strong wind |
| Union County | 41 km | Relatively Low | 55.4 | Earthquake |
Nearest by distance between county centres. Every county in Illinois, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Moderate 55.4 |
|---|---|
| Community resilience | Relatively High 78.2 |
| Community risk factor | 1.16 |
| Expected annual loss, all hazards | $53 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Williamson County's main hazards
- Right now: National Weather Service alerts for Illinois · all official warnings on Global Incident Tracker.
- Strong wind: Power outages now
- Earthquake: Earthquakes today · Earthquake safety guide
- Heat wave: Heatstroke warning signs
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Williamson County
What natural disasters is Williamson County, Illinois most at risk from?
Williamson County, Illinois has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 85.8 out of 100, higher than about 85% of US counties, with strong winds, earthquakes and heat waves scoring highest of its 18 hazards and $53 million a year in expected losses.
How many federal disaster declarations has Williamson County had?
OpenFEMA lists 7 federal disaster declarations that included Williamson County since 1982, not counting 2 for COVID-19; the latest is DR-1991-IL (Severe Storms and Flooding, declared 7 June 2011). Another 2 Illinois declarations were made statewide without a county list.
How many tornadoes have hit Williamson County?
NOAA's Storm Prediction Center recorded 23 tornadoes touching Williamson County from 1950 to 2025. The deadliest: 18 Dec 1957, F4, 28.3 mi path, 11 killed, 200 injured (deaths and injuries are for the whole path).
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.