St. Clair County, Illinois Natural Disaster Risk
FEMA National Risk Index assessment · IL
HighComposite Risk Score
National percentile: 95th
St. Clair County faces high composite natural disaster risk (NRI Risk Index score 94.9, 95th national percentile), driven primarily by heat wave and earthquake exposure. Expected annual loss across all 18 hazard types is $175M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
St. Clair County carries a high composite natural disaster risk, with a National Risk Index score of 94.9 out of 100 — placing it in the 95th national percentile and in the upper tier of natural-disaster risk nationally. 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 heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at High risk — $15M in expected annual loss and about 14.79 events per year; earthquake (ground shaking from sudden movement along geologic faults) at Medium risk — $51M in expected annual loss and about 0.01 events per year; and hail (ice stones from severe thunderstorms that damage property and crops) at High risk — $5M in expected annual loss and about 5.20 events per year. Across all hazards, FEMA estimates $175M in expected annual loss for a population of 257K.
Beyond physical exposure, St. Clair County has a low 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: St. Clair County has received 19 federal disaster declarations since 1968, including 8 for flood events and 5 for severe storm events. The most recent was Severe Storms, Tornadoes, Straight-Line Winds, and Floodng (flood), declared in September 2024.
Among 102 Illinois counties, St. Clair County ranks #5 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Heat Wave | High | 14.79 / yr | $15M |
| Earthquake | Medium | 0.01 / yr | $51M |
| Hail | High | 5.20 / yr | $5M |
| Cold Wave | High | 1.42 / yr | $15M |
| Tornado | High | 0.58 / yr | $13M |
| Riverine Flood | High | 1.79 / yr | $72M |
| Lightning | High | 51.93 / yr | $2M |
| Ice Storm | High | 1.39 / yr | $1M |
| Winter Weather | High | 9.00 / yr | $333K |
| Landslide | Low | 0.46 / yr | $28K |
| Drought | Low | 1.66 / yr | $314K |
| Strong Wind | Medium | 6.15 / yr | $627K |
| Hurricane | Very Low | 0.01 / yr | $21K |
| Wildfire | Very Low | 0.00 / yr | $5K |
| 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
St. Clair County has received 19 federal disaster declarations since 1968, most recently Severe Storms, Tornadoes, Straight-Line Winds, and Floodng in September 2024. Most frequent causes: Flood (8), Severe Storm (5), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| September 2024 | Flood | Severe Storms, Tornadoes, Straight-Line Winds, and Floodng |
| October 2022 | Flood | Severe Storm and Flooding |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2019 | Flood | Severe Storms and Flooding |
| June 2008 | Severe Storm | Severe Storms and Flooding |
| February 2007 | Severe Ice Storm | Severe Winter Storm |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| May 2002 | Tornado | Severe Storms, Tornadoes and Flooding |
| May 1996 | Severe Storm | Severe Storms and Flooding |
Showing the 10 most recent of 19 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for St. Clair County?
St. Clair County has a composite FEMA National Risk Index score of 94.9 out of 100, placing it in the High category and the 95th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in St. Clair County?
The three highest-rated hazards are Heat Wave (High, $15M EAL), Earthquake (Medium, $51M EAL), Hail (High, $5M EAL). These account for most of the county's expected annual losses.
How does St. Clair County compare to other Illinois counties?
St. Clair County ranks #5 of 102 Illinois counties for overall natural disaster risk, with a high rating.
How many federally declared disasters has St. Clair County had?
FEMA records 19 federal disaster declarations for St. Clair County since 1968, most often 8 for flood events and 5 for severe storm events. The most recent was Severe Storms, Tornadoes, Straight-Line Winds, and Floodng, declared in September 2024.
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. St. Clair County's $175M EAL is a statistical average, not a guarantee for any specific year or address.