Mercer County, Illinois
Natural disaster risk, federal disaster history and flood insurance facts.
Mercer County, Illinois has a very low overall risk from natural hazards in FEMA's National Risk Index. Its risk score is lower than 91% of US counties. It ranks 97th of 102 counties in Illinois. The costliest hazards here are inland flooding, strong wind and drought. FEMA estimates about $6.9 million a year in expected losses, or roughly $443 per resident. Since 1965 it has been included in 13 federal disaster or emergency declarations for natural events (10 major disasters). The most recent was in September 2019 (severe storms and flooding). Only 15 homes here carry federal flood insurance. Since 1978, federal flood insurance has paid about $1.4 million on 61 claims here, including $769,000 for floods in 1993.
FEMA National Risk Index December 2025; OpenFEMA declarations to Nov 6, 2026; NFIP records. Updated November 6, 2026.
Top risks in Mercer County
- Check the FEMA flood map for your address, and ask the seller or landlord about past flooding.
- Price a flood policy now. Most new federal policies take 30 days to start.
- Secure outdoor furniture and trash bins before storms.
- Have trees near the house checked.
- Check local water restrictions.
- Choose drought-tolerant plants.
All 18 hazards
What the ratings mean ›| Hazard | Rating | Score | Expected loss a year | |
|---|---|---|---|---|
| Inland flooding | 9.2 | $2M | ||
| Strong wind | 61.6 | $1M | ||
| Drought | 71.5 | $907K | ||
| Cold wave | 33.4 | $777K | ||
| Heat wave | 48.5 | $551K | ||
| Lightning | 58.1 | $492K | ||
| Tornado | 22.5 | $467K | ||
| Ice storm | 66.3 | $285K | ||
| Hail | 29.5 | $182K | ||
| Earthquake | 24.7 | $69K | ||
| Winter weather | 26.9 | $40K | ||
| Landslide | 68.1 | $8K | ||
| Hurricane | 11.3 | $4K | ||
| Wildfire | 1.1 | $719 |
Scores are percentiles: a score of 90 means higher risk than about 90% of US counties for that hazard. Hazards FEMA does not rate here are left out. Social vulnerability is very low and community resilience is very high in FEMA's measures.
Federal disaster history
Recent disasters nationwide ›Declarations by decade
Federal declarations for natural events that included Mercer County. 2020s bar runs to November 2026.
By type
Most recent
Show all 13
Illinois also had 2 statewide declarations that did not name single counties.
Storm history since 1952
Tornado risk by county ›The National Weather Service has logged 334 storm reports in Mercer County since 1952, with 1 death and 6 injuries and about $37.8 million in reported damage. The strongest on record here was an F3 tornado on August 15, 1978.
Strongest tornadoes
| Date | Strength | Near | Hurt / killed |
|---|---|---|---|
| Aug 15, 1978 | F3 | – | 0 / 0 |
| Jun 14, 1974 | F3 | – | 1 / 0 |
| Apr 21, 1973 | F2 | – | 0 / 0 |
| Jun 18, 1998 | F2 | Seaton | 0 / 0 |
| Apr 13, 2006 | F2 | Matherville | 0 / 0 |
Most damaging storms
| Date | Type | Near | Damage |
|---|---|---|---|
| Jul 20, 2003 | Thunderstorm Wind | Countywide | $13M |
| Apr 30, 2003 | Flash Flood | Countywide | $10M |
| May 13, 2010 | Flash Flood | Eliza | $5M |
| Apr 21, 1973 | Tornado | – | $3M |
| Apr 30, 2003 | Hail | New Boston | $500K |
| Apr 30, 2003 | Tornado | Aledo | $500K |
Source: NOAA Storm Events Database, county-based reports through Jun 17, 2026. Tornado records start in 1950, hail and wind in 1955, and floods and other storm types in 1996, so older decades undercount. Damage is in dollars of the year it happened and is often an estimate. Winter storms, heat and hurricanes are logged by forecast zone, not county, so they are not counted here.
Flood insurance in Mercer County
Check your address flood zone ›National Flood Insurance Program (NFIP) records only; private flood policies are not included. Home counts as of Aug 3, 2026. Since 2021 NFIP prices each home separately under Risk Rating 2.0, so your price depends on the building, not the county. Ask an agent for a quote.
Homes in Mercer County
Older homes and mobile homes usually suffer more damage in storms, floods and earthquakes, and can cost more to insure. If you are buying, ask about roof age, foundation bolting and any retrofits. Source: US Census Bureau, American Community Survey 2020 to 2024 5-year estimates; 7,285 housing units.
Compare in Illinois
All 102 ›| Largest counties | Overall risk | Top hazard |
|---|---|---|
| Cook County | Inland flooding | |
| DuPage County | Inland flooding | |
| Lake County | Inland flooding | |
| Will County | Inland flooding | |
| Kane County | Inland flooding | |
| McHenry County | Inland flooding | |
| Winnebago County | Inland flooding | |
| Madison County | Inland flooding |
Neighboring counties
| County | Overall risk | Declarations |
|---|---|---|
| Rock Island County | 13 | |
| Knox County | 9 | |
| Henry County | 14 | |
| Des Moines County, IA | 25 | |
| Warren County | 7 | |
| Louisa County, IA | 18 | |
| Henderson County | 14 |
Common questions about Mercer County
What is the biggest natural hazard in Mercer County?
Inland flooding has the highest expected yearly losses in Mercer County, about $2 million a year in FEMA's estimate. Strong wind is second at $1.2 million.
How many federal disasters has Mercer County had?
Mercer County has been included in 13 federal disaster or emergency declarations for natural events since 1965, including 10 major disasters. The most recent was Severe Storms and Flooding in September 2019.
Is Mercer County a high-risk place to live?
Its overall rating is Very Low, 97th highest of 102 in Illinois. A county rating covers the whole area. Risk at one address can be much higher or lower, so check the FEMA flood map and ask about the home's history.
Do I need flood insurance in Mercer County?
Standard home insurance does not cover flooding. About 1 in 500 homes in Mercer County has federal flood insurance. Lenders require it in mapped high-risk zones, but many flood claims come from outside those zones.
How many tornadoes has Mercer County had?
NOAA records list 45 tornadoes in Mercer County since 1950. The strongest was an F3 tornado on August 15, 1978. The weather service has also logged 96 hail reports and 48 floods here.
Sources: FEMA National Risk Index (December 2025), OpenFEMA Disaster Declarations Summaries, and NFIP policy and claims data. Hazard Compass is independent and not affiliated with FEMA. These figures describe the whole county, not a single property, and are not insurance or safety advice. Report a problem.