Johnson County, Iowa
Natural disaster risk, federal disaster history and flood insurance facts.
Johnson County, Iowa has a moderate overall risk from natural hazards in FEMA's National Risk Index. Its risk score is higher than 87% of US counties. It ranks 2nd of 99 counties in Iowa. The costliest hazards here are tornadoes, inland flooding and strong wind. FEMA estimates about $96 million a year in expected losses, or roughly $630 per resident. Since 1965 it has been included in 22 federal disaster or emergency declarations for natural events (21 major disasters). The most recent was in August 2020 (severe storms). Fewer than 1 in 100 homes here carry federal flood insurance (360 policies). Since 1978, federal flood insurance has paid about $32 million on 446 claims here, including $27 million for floods in 2008.
FEMA National Risk Index December 2025; OpenFEMA declarations to Nov 6, 2026; NFIP records. Updated November 6, 2026.
Top risks in Johnson County
- Pick a shelter spot: a basement, or an inside room on the lowest floor with no windows.
- Turn on emergency alerts on your phone and keep a weather radio.
- 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.
All 18 hazards
What the ratings mean ›| Hazard | Rating | Score | Expected loss a year | |
|---|---|---|---|---|
| Tornado | 98.2 | $36M | ||
| Inland flooding | 79.8 | $27M | ||
| Strong wind | 98.9 | $10M | ||
| Cold wave | 90.3 | $10M | ||
| Hail | 95.3 | $4M | ||
| Heat wave | 87.5 | $4M | ||
| Drought | 81.8 | $1M | ||
| Lightning | 74.5 | $830K | ||
| Winter weather | 87.9 | $492K | ||
| Ice storm | 75.7 | $428K | ||
| Earthquake | 45.1 | $294K | ||
| Wildfire | 64.4 | $164K | ||
| Landslide | 79.1 | $20K | ||
| Hurricane | 13.6 | $5K |
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 Johnson County. 2020s bar runs to November 2026.
By type
Most recent
Show all 22
Iowa also had 11 statewide declarations that did not name single counties.
Storm history since 1958
Tornado risk by county ›The National Weather Service has logged 642 storm reports in Johnson County since 1958, with 2 deaths and 67 injuries and about $353 million in reported damage. The strongest on record here was an F3 tornado on May 15, 1998 near Hills.
Strongest tornadoes
| Date | Strength | Near | Hurt / killed |
|---|---|---|---|
| May 15, 1998 | F3 | Hills | 17 / 0 |
| May 22, 1962 | F2 | – | 0 / 1 |
| Apr 13, 2006 | F2 | Iowa City | 30 / 0 |
| Apr 21, 1973 | F2 | – | 0 / 0 |
| Jun 7, 1984 | F2 | – | 0 / 0 |
Most damaging storms
| Date | Type | Near | Damage |
|---|---|---|---|
| Jun 1, 2008 | Flood | Kent County Park | $230M |
| Jun 29, 1998 | Thunderstorm Wind | Countywide | $45M |
| May 18, 1997 | Hail | Iowa City | $40M |
| Apr 13, 2006 | Tornado | Iowa City | $12M |
| May 15, 1998 | Tornado | Hills | $6M |
| Apr 21, 1973 | Tornado | – | $3M |
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 Johnson 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 Johnson 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; 68,217 housing units.
Compare in Iowa
All 99 ›| Largest counties | Overall risk | Top hazard |
|---|---|---|
| Polk County | Inland flooding | |
| Linn County | Inland flooding | |
| Scott County | Inland flooding | |
| Johnson County | Tornado | |
| Black Hawk County | Inland flooding | |
| Woodbury County | Inland flooding | |
| Dallas County | Inland flooding | |
| Dubuque County | Inland flooding |
Neighboring counties
| County | Overall risk | Declarations |
|---|---|---|
| Linn County | 21 | |
| Muscatine County | 19 | |
| Benton County | 16 | |
| Washington County | 13 | |
| Cedar County | 16 | |
| Iowa County | 21 | |
| Louisa County | 18 |
Cities in Johnson County
Common questions about Johnson County
What is the biggest natural hazard in Johnson County?
Tornado has the highest expected yearly losses in Johnson County, about $36.2 million a year in FEMA's estimate. Inland flooding is second at $27.5 million.
How many federal disasters has Johnson County had?
Johnson County has been included in 22 federal disaster or emergency declarations for natural events since 1965, including 21 major disasters. The most recent was Severe Storms in August 2020.
Is Johnson County a high-risk place to live?
Its overall rating is Relatively Moderate, 2nd highest of 99 in Iowa. 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 Johnson County?
Standard home insurance does not cover flooding. About 1 in 143 homes in Johnson 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 Johnson County had?
NOAA records list 46 tornadoes in Johnson County since 1950. The strongest was an F3 tornado on May 15, 1998 near Hills. The weather service has also logged 229 hail reports and 67 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.