Mercer County, Ohio Natural Disaster Risk
FEMA National Risk Index assessment · OH
Very LowComposite Risk Score
National percentile: 32th
Mercer County faces very low composite natural disaster risk (NRI Risk Index score 31.6, 32th national percentile), driven primarily by earthquake and tornado exposure. Expected annual loss across all 18 hazard types is $18M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Mercer County is very low, with a National Risk Index score of 31.6 out of 100 — placing it in the 32nd 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 earthquake (ground shaking from sudden movement along geologic faults) at Low risk — $2M in expected annual loss and about 0.00 events per year; tornado (violently rotating columns of air capable of catastrophic local damage) at Medium risk — $4M in expected annual loss and about 0.31 events per year; and hail (ice stones from severe thunderstorms that damage property and crops) at Low risk — $769K in expected annual loss and about 3.46 events per year. Across all hazards, FEMA estimates $18M in expected annual loss for a population of 43K.
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 14 federal disaster declarations since 1965, including 6 for severe storm events and 3 for tornado events. The most recent was Tornadoes (tornado), declared in May 2024.
Among 88 Ohio counties, Mercer County ranks #73 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | Low | 0.00 / yr | $2M |
| Tornado | Medium | 0.31 / yr | $4M |
| Hail | Low | 3.46 / yr | $769K |
| Strong Wind | Low | 3.51 / yr | $941K |
| Ice Storm | Low | 0.79 / yr | $119K |
| Riverine Flood | Low | 2.25 / yr | $9M |
| Hurricane | Very Low | 0.01 / yr | $49K |
| Cold Wave | Low | 4.84 / yr | $759K |
| Winter Weather | Low | 11.74 / yr | $48K |
| Lightning | Low | 42.85 / yr | $162K |
| Landslide | Very Low | 0.08 / yr | $225 |
| Heat Wave | Very Low | 4.00 / yr | $83K |
| Wildfire | Very Low | 0.00 / yr | $4K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Drought | 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 14 federal disaster declarations since 1965, most recently Tornadoes in May 2024. Most frequent causes: Severe Storm (6), Tornado (3), Biological (2).
| Declared | Type | Disaster |
|---|---|---|
| May 2024 | Tornado | Tornadoes |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| June 2019 | Tornado | Severe Storms, Straight-Line Winds, Tornadoes, Flooding, Landslides, and Mudslide |
| June 2012 | Severe Storm | Severe Storms |
| September 2005 | Hurricane | Hurricane Katrina Evacuation |
| February 2005 | Severe Storm | Severe Winter Storms, Flooding, and Mudslides |
| September 2004 | Severe Storm | Severe Storms and Flooding |
| July 2003 | Severe Storm | Severe Storms and Flooding |
| August 1995 | Severe Storm | Severe Storms and Flooding |
Showing the 10 most recent of 14 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 31.6 out of 100, placing it in the Very Low category and the 32th 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 Earthquake (Low, $2M EAL), Tornado (Medium, $4M EAL), Hail (Low, $769K EAL). These account for most of the county's expected annual losses.
How does Mercer County compare to other Ohio counties?
Mercer County ranks #73 of 88 Ohio counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Mercer County had?
FEMA records 14 federal disaster declarations for Mercer County since 1965, most often 6 for severe storm events and 3 for tornado events. The most recent was Tornadoes, declared in May 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. Mercer County's $18M EAL is a statistical average, not a guarantee for any specific year or address.