Johnson County, Illinois Natural Disaster Risk
FEMA National Risk Index assessment · IL
LowComposite Risk Score
National percentile: 51th
Johnson County faces low composite natural disaster risk (NRI Risk Index score 51.1, 51th national percentile), driven primarily by earthquake and heat wave exposure. Expected annual loss across all 18 hazard types is $12M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Johnson County is low, with a National Risk Index score of 51.1 out of 100 — placing it in the 51st national percentile and below the national average for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Johnson County's expected losses come from earthquake (ground shaking from sudden movement along geologic faults) at Medium risk — $4M in expected annual loss and about 0.01 events per year; heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Low risk — $623K in expected annual loss and about 10.47 events per year; and strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at Medium risk — $676K in expected annual loss and about 4.04 events per year. Across all hazards, FEMA estimates $12M in expected annual loss for a population of 13K.
Beyond physical exposure, Johnson County has a very high social vulnerability rating (how susceptible the population is to harm) and a medium community resilience rating (its capacity to prepare for and recover from disasters). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
The county's disaster history tells the same story: Johnson County has received 7 federal disaster declarations since 1973, including 2 for biological events and 1 for severe storm events. The most recent was Covid-19 Pandemic (biological), declared in March 2020.
Among 102 Illinois counties, Johnson County ranks #58 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | Medium | 0.01 / yr | $4M |
| Heat Wave | Low | 10.47 / yr | $623K |
| Strong Wind | Medium | 4.04 / yr | $676K |
| Ice Storm | Medium | 0.91 / yr | $145K |
| Hail | Low | 3.20 / yr | $346K |
| Winter Weather | Medium | 7.47 / yr | $76K |
| Cold Wave | Low | 1.11 / yr | $1M |
| Tornado | Low | 0.30 / yr | $1M |
| Drought | Low | 4.02 / yr | $125K |
| Landslide | Very Low | 0.82 / yr | $636 |
| Hurricane | Very Low | 0.02 / yr | $19K |
| Riverine Flood | Low | 0.82 / yr | $3M |
| Lightning | Low | 55.10 / yr | $91K |
| Wildfire | Very Low | 0.00 / yr | $3K |
| 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
Johnson County has received 7 federal disaster declarations since 1973, most recently Covid-19 Pandemic in March 2020. Most frequent causes: Biological (2), Severe Storm (1), Hurricane (1).
| Declared | Type | Disaster |
|---|---|---|
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| March 2009 | Severe Storm | Severe Winter Storm |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| February 2005 | Snowstorm | Record/Near Record Snow |
| May 2002 | Tornado | Severe Storms, Tornadoes and Flooding |
| April 1973 | Flood | Severe Storms & Flooding |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Johnson County?
Johnson County has a composite FEMA National Risk Index score of 51.1 out of 100, placing it in the Low category and the 51th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Johnson County?
The three highest-rated hazards are Earthquake (Medium, $4M EAL), Heat Wave (Low, $623K EAL), Strong Wind (Medium, $676K EAL). These account for most of the county's expected annual losses.
How does Johnson County compare to other Illinois counties?
Johnson County ranks #58 of 102 Illinois counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Johnson County had?
FEMA records 7 federal disaster declarations for Johnson County since 1973, most often 2 for biological events and 1 for severe storm 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. Johnson County's $12M EAL is a statistical average, not a guarantee for any specific year or address.