Cass County, Iowa
Natural disaster risk, federal disaster history and flood insurance facts.
Cass County, Iowa has a relatively low overall risk from natural hazards in FEMA's National Risk Index. Its risk score is higher than 60% of US counties. It ranks 17th of 99 counties in Iowa. The costliest hazards here are cold waves, inland flooding and drought. FEMA estimates about $17 million a year in expected losses, or roughly $1,264 per resident. Since 1965 it has been included in 17 federal disaster or emergency declarations for natural events (15 major disasters). The most recent was in February 2022 (severe storms, straight-line winds and tornadoes). Only 19 homes here carry federal flood insurance. Since 1978, federal flood insurance has paid about $335,000 on 57 claims here.
FEMA National Risk Index December 2025; OpenFEMA declarations to Nov 6, 2026; NFIP records. Updated November 6, 2026.
Top risks in Cass County
- Insulate pipes in outside walls, crawl spaces and garages.
- Know how to shut off the main water valve.
- 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.
- Check local water restrictions.
- Choose drought-tolerant plants.
All 18 hazards
What the ratings mean ›| Hazard | Rating | Score | Expected loss a year | |
|---|---|---|---|---|
| Cold wave | 86.9 | $4M | ||
| Inland flooding | 43.4 | $4M | ||
| Drought | 97.6 | $3M | ||
| Tornado | 75.8 | $3M | ||
| Heat wave | 71.8 | $775K | ||
| Hail | 79.5 | $662K | ||
| Strong wind | 60.9 | $584K | ||
| Ice storm | 56.4 | $88K | ||
| Winter weather | 48.2 | $47K | ||
| Lightning | 17.6 | $47K | ||
| Wildfire | 40.6 | $21K | ||
| Earthquake | 16.2 | $15K | ||
| Hurricane | 17.6 | $4K | ||
| Landslide | 65.5 | $3K |
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 relatively high 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 Cass County. 2020s bar runs to November 2026.
By type
Most recent
Show all 17
Iowa also had 11 statewide declarations that did not name single counties.
Storm history since 1956
Tornado risk by county ›The National Weather Service has logged 546 storm reports in Cass County since 1956, with 0 deaths and 11 injuries and about $40 million in reported damage. The strongest on record here was an F3 tornado on April 8, 1999 near Massena.
Strongest tornadoes
| Date | Strength | Near | Hurt / killed |
|---|---|---|---|
| Apr 8, 1999 | F3 | Massena | 0 / 0 |
| Apr 20, 1964 | F3 | – | 1 / 0 |
| Jun 7, 1984 | F2 | – | 8 / 0 |
| May 6, 2007 | EF2 | Griswold | 0 / 0 |
| Dec 15, 2021 | EF2 | Lewis | 0 / 0 |
Most damaging storms
| Date | Type | Near | Damage |
|---|---|---|---|
| Jun 12, 2010 | Flood | Marne | $20M |
| Jun 14, 1998 | Flash Flood | Atlantic | $3M |
| Jun 7, 1984 | Tornado | – | $3M |
| Jun 21, 1997 | Thunderstorm Wind | Cumberland | $1M |
| May 6, 2007 | Flood | Anita | $1M |
| May 6, 2007 | Tornado | Griswold | $1M |
Source: NOAA Storm Events Database, county-based reports through Jul 7, 2025. 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 Cass 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 Cass 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; 6,393 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 |
|---|---|---|
| Pottawattamie County | 24 | |
| Shelby County | 18 | |
| Guthrie County | 15 | |
| Montgomery County | 18 | |
| Adair County | 15 | |
| Audubon County | 20 | |
| Adams County | 15 |
Common questions about Cass County
What is the biggest natural hazard in Cass County?
Cold wave has the highest expected yearly losses in Cass County, about $4.3 million a year in FEMA's estimate. Inland flooding is second at $4.2 million.
How many federal disasters has Cass County had?
Cass County has been included in 17 federal disaster or emergency declarations for natural events since 1965, including 15 major disasters. The most recent was Severe Storms, Straight-Line Winds, and Tornadoes in February 2022.
Is Cass County a high-risk place to live?
Its overall rating is Relatively Low, 17th 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 Cass County?
Standard home insurance does not cover flooding. About 1 in 333 homes in Cass 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 Cass County had?
NOAA records list 40 tornadoes in Cass County since 1950. The strongest was an F3 tornado on April 8, 1999 near Massena. The weather service has also logged 174 hail reports and 44 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.