Williamson County, Illinois Natural Disaster Risk
FEMA National Risk Index assessment · IL
MediumComposite Risk Score
National percentile: 86th
Williamson County faces medium composite natural disaster risk (NRI Risk Index score 85.8, 86th national percentile), driven primarily by strong wind and earthquake exposure. Expected annual loss across all 18 hazard types is $53M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Williamson County carries a medium composite natural disaster risk, with a National Risk Index score of 85.8 out of 100 — placing it in the 86th national percentile and near the national midpoint for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
The county's risk is driven primarily by strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at Very High risk — $7M in expected annual loss and about 4.08 events per year; earthquake (ground shaking from sudden movement along geologic faults) at Medium risk — $20M in expected annual loss and about 0.01 events per year; and heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Medium risk — $3M in expected annual loss and about 10.37 events per year. Across all hazards, FEMA estimates $53M in expected annual loss for a population of 67K.
Beyond physical exposure, Williamson County has a medium social vulnerability rating (how susceptible the population is to harm) and a high community resilience rating (its capacity to prepare for and recover from disasters). A less vulnerable population paired with strong resilience helps the community absorb and recover from events.
The federal record bears this out: Williamson County has received 9 federal disaster declarations since 1982, including 3 for severe storm events and 2 for biological events. The most recent was Covid-19 Pandemic (biological), declared in March 2020.
Among 102 Illinois counties, Williamson County ranks #17 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Strong Wind | Very High | 4.08 / yr | $7M |
| Earthquake | Medium | 0.01 / yr | $20M |
| Heat Wave | Medium | 10.37 / yr | $3M |
| Winter Weather | High | 7.63 / yr | $364K |
| Cold Wave | Medium | 1.16 / yr | $5M |
| Ice Storm | Medium | 0.79 / yr | $428K |
| Tornado | Medium | 0.37 / yr | $4M |
| Landslide | Low | 0.47 / yr | $13K |
| Hail | Medium | 3.27 / yr | $721K |
| Riverine Flood | Low | 2.04 / yr | $12M |
| Lightning | Medium | 52.94 / yr | $409K |
| Drought | Low | 3.23 / yr | $178K |
| Hurricane | Very Low | 0.02 / yr | $39K |
| Wildfire | Very Low | 0.00 / yr | $4K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Williamson County has received 9 federal disaster declarations since 1982, most recently Covid-19 Pandemic in March 2020. Most frequent causes: Severe Storm (3), Biological (2), Tornado (2).
| Declared | Type | Disaster |
|---|---|---|
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| June 2011 | Severe Storm | Severe Storms and Flooding |
| July 2009 | Severe Storm | Severe Storms, Flooding, and Tornadoes |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| February 2005 | Snowstorm | Record/Near Record Snow |
| May 2002 | Tornado | Severe Storms, Tornadoes and Flooding |
| May 1996 | Severe Storm | Severe Storms and Flooding |
| June 1982 | Tornado | Severe Storms & Tornadoes |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Williamson County?
Williamson County has a composite FEMA National Risk Index score of 85.8 out of 100, placing it in the Medium category and the 86th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Williamson County?
The three highest-rated hazards are Strong Wind (Very High, $7M EAL), Earthquake (Medium, $20M EAL), Heat Wave (Medium, $3M EAL). These account for most of the county's expected annual losses.
How does Williamson County compare to other Illinois counties?
Williamson County ranks #17 of 102 Illinois counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Williamson County had?
FEMA records 9 federal disaster declarations for Williamson County since 1982, most often 3 for severe storm events and 2 for biological events. The most recent was Covid-19 Pandemic, declared in March 2020.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. Williamson County's $53M EAL is a statistical average, not a guarantee for any specific year or address.