riskbycounty
FEMA NRI 1.19.0Updated Nov 2023 · Coverage 2014–2023Methodology

Williamson County Disaster Risk

Williamson County, Illinois

FEMA Risk Rating

Relatively Moderate

National Percentile

86th

of 3,144 counties

State Rank

#17

of 102 (1 = highest risk)

Flood Risk

70th

percentile

Hazard Risk Breakdown

Flood

River, coastal, and surface flooding risk

Relatively Low

Higher than 70% of US counties

Wildfire

Wildland and wildland-urban interface fire risk

Very Low

Higher than 14% of US counties

Tornado

Tornado and severe thunderstorm risk

Relatively Low

Higher than 80% of US counties

Earthquake

Seismic activity and ground shaking risk

Relatively High

Higher than 96% of US counties

Hurricane

Tropical cyclone and hurricane risk

Relatively Low

Higher than 45% of US counties

Risk Overview

About Natural Disaster Risk in Williamson County, Illinois

Williamson faces above-average disaster risk

Williamson County's composite risk score of 85.78 significantly exceeds the state average (54.46) and ranks in the "Relatively Moderate" category—placing it in the upper tier of hazard exposure nationwide. This southern Illinois county experiences substantially elevated natural disaster risk.

Among Illinois's riskiest counties

Williamson County ranks in the top tier of Illinois counties for disaster risk, exceeding the state average by 57%. It is notably more exposed than most Illinois counties but below the very highest-risk counties.

Riskier than many regional peers

Williamson County's score of 85.78 substantially exceeds nearby Saline County and White County (54.26). Only Gallatin and similar extreme southern Illinois counties approach comparable risk levels.

Earthquakes and tornadoes dominate threats

Earthquake risk (96.34) and tornado risk (80.31) drive Williamson County's elevated composite score, reflecting the region's seismic and severe weather vulnerability. Flood risk (69.94) and hurricane risk (44.51) add secondary concerns.

Earthquake coverage is critical here

With earthquake risk at 96.34, Williamson County residents should prioritize standalone earthquake insurance—the highest level available given the seismic zone exposure. Confirm tornado and wind coverage are comprehensive given the 80.31 tornado risk score.

Source: FEMA National Risk Index · Narrative reviewed by Evan Brooks, Data Editor

Preparedness Guide

What to Prepare for in Williamson County

Top Hazards by Exposure

  1. #1
    EarthquakePrepare
    96th percentile
  2. #2
    TornadoPrepare
    80th percentile
  3. #3
    FloodPrepare
    70th percentile

Source: FEMA National Risk Index v1.19.0 · Percentiles are national (3,144 counties)

Local Resources

Risk Advisory: Williamson County

Risk Verdict

Williamson County faces a moderate natural disaster risk profile, ranking at the 86th percentile nationally under FEMA's composite risk model. This risk level calls for more than general awareness: insurance coverage review, a family communication plan, and a prepared go-bag are practical priorities.

Hazard Breakdown

Earthquake risk is Williamson County's dominant natural hazard, ranked at the 96th percentile nationally under FEMA's National Risk Index. Tornado ranks second at the 80th percentile nationally. Additional tracked hazards include flood (70th percentile), hurricane (45th percentile), wildfire (14th percentile).

Preparedness Context

Earthquake risk is Williamson County's leading natural hazard, ranked at the 96th percentile nationally. Securing tall furniture, water heaters, and bookcases to walls with anti-tip hardware is among the simplest and most effective life-safety measures households can take. Alongside earthquake exposure, Williamson County's tornado risk at the 80th percentile nationally reinforces the value of maintaining a household emergency supply cache usable for multiple hazard scenarios. Williamson County residents should locate the main gas shutoff valve and keep an appropriate wrench nearby — gas leaks cause a significant share of earthquake-related injuries and fires, and the shutoff step is safe to take immediately after shaking stops.

Regional Context

Williamson County's composite risk score sits 31.3 points above the Illinois county average, placing it among the more hazard-exposed counties in the state.

Is your household prepared for Williamson County's hazards?

Review FEMA's county-specific preparedness checklists and emergency planning guides.

FEMA Ready Guide →

Frequently Asked Questions

What is the natural disaster risk in Williamson County, IL?
Williamson County has a FEMA National Risk Index rating of Relatively Moderate, placing it in the 86th percentile nationally out of 3,144 counties. This composite score reflects the county's overall exposure to natural hazards including floods, wildfires, tornadoes, earthquakes, and hurricanes, weighted by expected annual loss and social vulnerability.
What types of natural hazards affect Williamson County?
Williamson County is evaluated for five major natural hazard types: earthquake (96th percentile), tornado (80th percentile), flooding (70th percentile), hurricane (45th percentile), wildfire (14th percentile). The highest-risk hazard is earthquake at the 96th percentile nationally. These scores are derived from FEMA's National Risk Index, which analyzes expected annual loss, social vulnerability, and community resilience for each hazard type.
How does Williamson County risk compare to the Illinois average?
Williamson County's composite risk percentile is 86th, compared to the Illinois state average of 55th percentile. The state's overall risk rating is Relatively Low. This means Williamson County faces higher natural disaster risk than the typical county in Illinois.
Is Williamson County at risk for earthquake?
Yes, Williamson County's earthquake risk is at the 96th percentile nationally. This places it in the top quartile for this hazard type. For flooding specifically, Williamson County is at the 70th percentile.
How is natural disaster risk measured?
FEMA's National Risk Index (NRI) calculates risk scores for 18 natural hazard types across all U.S. counties and census tracts. The composite score combines Expected Annual Loss (estimated dollar losses from each hazard), Social Vulnerability (demographic factors affecting disaster impact), and Community Resilience (ability to recover). Percentile scores rank each county against all 3,144 U.S. counties, and risk ratings range from Very Low to Very High.
Why is Williamson County higher risk than average?
Williamson County's composite risk score of 86th percentile is above the Illinois state average of 55th percentile. This elevated risk is driven by earthquake exposure (96th percentile), along with tornado and flooding risk. Geographic location, terrain, climate patterns, and proximity to flood zones or fault lines all influence a county's risk profile.

Counties with Similar Risk

LaSalle County

Illinois

+0.3

Relatively Moderate

86th percentile

McLean County

Illinois

+1.1

Relatively Moderate

87th percentile

Jackson County

Illinois

+1.3

Relatively Moderate

87th percentile

By Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

Data Source

Risk data sourced from the FEMA National Risk Index (NRI). Risk scores are relative rankings (0–100) across all US counties — not absolute risk measures. Higher scores indicate higher relative risk compared to other counties.

Disclaimer: This data is informational only. It is not financial, insurance, or legal advice. Always consult a qualified professional before making insurance or real estate decisions.

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