Cassia County, Idaho: Natural Disaster Risk and History
Cassia County, Idaho has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 43.6 out of 100, higher than about 43% of US counties, with wildfires, winter storms and earthquakes scoring highest of its 18 hazards and $16 million a year in expected losses.
OpenFEMA lists 3 federal disaster declarations that included Cassia County since 1964, not counting 2 for COVID-19; the latest is DR-4310-ID (Severe Winter Storms and Flooding, declared 21 April 2017). NOAA's Storm Prediction Center recorded 10 tornadoes touching Cassia County from 1950 to 2025.
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Population 24,356 Buildings worth $8.5 billion Area 2,607 sq mi Risk rank in Idaho 19 of 44 FIPS 16031
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Wildfire | Relatively Moderate | 94.7 | $3.7 million | about once every 73 years | — |
| Winter weather | Relatively Moderate | 81.9 | $258,902 | about 15 a year | 291 |
| Earthquake | Relatively Low | 74.5 | $1.2 million | about once every 119 years | — |
| Lightning | Relatively Moderate | 69.1 | $547,125 | about 28 a year | 46,866 strikes |
| Avalanche | Very Low | 56.9 | $1,291 | about once every 100 years | 0 |
| Heat wave | Relatively Low | 56.6 | $571,957 | about 2.5 a year | 38 |
| Inland flooding | Relatively Low | 52.7 | $8.1 million | about once every 1.3 years | 21 |
| Landslide | Very Low | 49.5 | $1,467 | about once every 1.2 years | — |
| Volcanic activity | Very Low | 47.2 | $12 | rarer than once in 1,000 years | 3 |
| Cold wave | Relatively Low | 42.7 | $822,603 | about once every 2.6 years | 7.4 |
| Drought | Very Low | 25.2 | $14,724 | about 64 a year | 1,785 |
| Strong wind | Relatively Low | 23.2 | $243,778 | about once every 1.9 years | 20 |
| Ice storm | Very Low | 13.8 | $9,324 | about once every 67 years | 0 |
| Hail | Very Low | 10.9 | $39,579 | about once every 3.3 years | 11 |
| Tornado | Very Low | 9.8 | $70,274 | about once every 4.5 years | 10 |
| Coastal flooding | Not Applicable | — | — | — | — |
| Hurricane | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 3
Most common: Flood 2, Hurricane 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 1 | Flood |
| 2000s | 1 | Hurricane |
| 2010s | 1 | Flood |
The last 3
Widest declarations that included Cassia County
- Hurricane Katrina (2005, EM-3244-ID): 44 Idaho counties designated.
- Heavy Rains & Flooding (1964, DR-186-ID): 27 Idaho counties designated.
- Severe Winter Storms and Flooding (2017, DR-4310-ID): 11 Idaho counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Idaho also had 8 statewide declarations with no county list.
Tornado record since 1950 10
| Tornadoes touching the county | 10 |
|---|---|
| Strongest-rated | (E)F0 ×10 |
| Peak month | June (3) |
| Deadliest | — |
| Longest path | 24 Jun 2004, F0, 1 mi path |
| Most recent | 26 May 2023, EF0, 0.2 mi path |
| Deaths / injuries on those paths | 0 / 0 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 10 | 0 | 0 | 0 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 0 | 0 | 0 | 1 | 3 | 2 | 3 | 1 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Cassia County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Cassia County (this page) | — | Relatively Low | 43.6 | Wildfire |
| Minidoka County | 64 km | Very Low | 20.5 | Winter weather |
| Jerome County | 71 km | Very Low | 21.5 | Wildfire |
| Power County | 77 km | Very Low | 16.9 | Wildfire |
| Oneida County | 88 km | Very Low | 1.4 | Wildfire |
| Twin Falls County | 88 km | Relatively Low | 46.9 | Winter weather |
Nearest by distance between county centres. Every county in Idaho, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 22.4 |
|---|---|
| Community resilience | Relatively Low 20.8 |
| Community risk factor | 0.92 |
| Expected annual loss, all hazards | $16 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Cassia County's main hazards
- Right now: National Weather Service alerts for Idaho · all official warnings on Global Incident Tracker.
- Wildfire: US wildfires now · Wildfire smoke: what protects you
- Winter weather: Power outages now · Carbon monoxide in winter
- Earthquake: Earthquakes today · Earthquake safety guide
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Cassia County
What natural disasters is Cassia County, Idaho most at risk from?
Cassia County, Idaho has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 43.6 out of 100, higher than about 43% of US counties, with wildfires, winter storms and earthquakes scoring highest of its 18 hazards and $16 million a year in expected losses.
How many federal disaster declarations has Cassia County had?
OpenFEMA lists 3 federal disaster declarations that included Cassia County since 1964, not counting 2 for COVID-19; the latest is DR-4310-ID (Severe Winter Storms and Flooding, declared 21 April 2017). Another 8 Idaho declarations were made statewide without a county list.
How many tornadoes have hit Cassia County?
NOAA's Storm Prediction Center recorded 10 tornadoes touching Cassia County from 1950 to 2025.
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.