Mercer County, Illinois Natural Disaster Risk
FEMA National Risk Index assessment · IL
Very LowComposite Risk Score
National percentile: 9th
Mercer County faces very low composite natural disaster risk (NRI Risk Index score 8.8, 9th national percentile), driven primarily by drought and landslide exposure. Expected annual loss across all 18 hazard types is $7M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Mercer County at very low composite risk, with a National Risk Index score of 8.8 out of 100 — placing it in the 9th national percentile and among the lowest-risk counties in the country. 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 drought (extended dry periods that stress water supplies and agriculture) at Medium risk — $907K in expected annual loss and about 8.21 events per year; landslide (downhill movement of rock, soil, and debris on unstable slopes) at Low risk — $8K in expected annual loss and about 0.24 events per year; and ice storm (freezing rain that coats surfaces in heavy, damaging ice) at Medium risk — $285K in expected annual loss and about 0.67 events per year. Across all hazards, FEMA estimates $7M in expected annual loss for a population of 16K.
Beyond physical exposure, Mercer County has a very low social vulnerability rating (how susceptible the population is to harm) and a very 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: Mercer County has received 15 federal disaster declarations since 1965, including 7 for flood events and 3 for snowstorm events. The most recent was Covid-19 Pandemic (biological), declared in March 2020.
Among 102 Illinois counties, Mercer County ranks #97 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Drought | Medium | 8.21 / yr | $907K |
| Landslide | Low | 0.24 / yr | $8K |
| Ice Storm | Medium | 0.67 / yr | $285K |
| Strong Wind | Medium | 6.25 / yr | $1M |
| Lightning | Medium | 44.82 / yr | $492K |
| Heat Wave | Low | 8.16 / yr | $551K |
| Cold Wave | Low | 5.37 / yr | $777K |
| Hail | Very Low | 4.23 / yr | $182K |
| Winter Weather | Low | 14.16 / yr | $40K |
| Earthquake | Very Low | 0.00 / yr | $69K |
| Tornado | Very Low | 0.53 / yr | $467K |
| Hurricane | Very Low | 0.01 / yr | $4K |
| Riverine Flood | Very Low | 1.64 / yr | $2M |
| Wildfire | Very Low | 0.00 / yr | $719 |
| 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
Mercer County has received 15 federal disaster declarations since 1965, most recently Covid-19 Pandemic in March 2020. Most frequent causes: Flood (7), Snowstorm (3), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2019 | Flood | Severe Storms and Flooding |
| May 2013 | Flood | Severe Storms, Straight-Line Winds, and Flooding |
| March 2011 | Snowstorm | Severe Winter Storm and Snowstorm |
| June 2008 | Severe Storm | Severe Storms and Flooding |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| May 2001 | Flood | Flooding |
| January 1999 | Snowstorm | Il-Winter Storm 1/1/99 |
| July 1993 | Flood | Severe Storms & Flooding |
Showing the 10 most recent of 15 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Mercer County?
Mercer County has a composite FEMA National Risk Index score of 8.8 out of 100, placing it in the Very Low category and the 9th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Mercer County?
The three highest-rated hazards are Drought (Medium, $907K EAL), Landslide (Low, $8K EAL), Ice Storm (Medium, $285K EAL). These account for most of the county's expected annual losses.
How does Mercer County compare to other Illinois counties?
Mercer County ranks #97 of 102 Illinois counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Mercer County had?
FEMA records 15 federal disaster declarations for Mercer County since 1965, most often 7 for flood events and 3 for snowstorm 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. Mercer County's $7M EAL is a statistical average, not a guarantee for any specific year or address.