Cassia County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
LowComposite Risk Score
National percentile: 44th
Cassia County faces low composite natural disaster risk (NRI Risk Index score 43.6, 44th national percentile), driven primarily by wildfire and winter weather exposure. Expected annual loss across all 18 hazard types is $16M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Cassia County is low, with a National Risk Index score of 43.6 out of 100 — placing it in the 44th national percentile and below the national average for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Most of Cassia County's expected losses come from wildfire (uncontrolled fires that spread across wildland and into communities) at Medium risk — $4M in expected annual loss and about 0.01 events per year; winter weather (heavy snow, blizzards, and hazardous winter conditions) at Medium risk — $259K in expected annual loss and about 15.31 events per year; and earthquake (ground shaking from sudden movement along geologic faults) at Low risk — $1M in expected annual loss and about 0.01 events per year. Across all hazards, FEMA estimates $16M in expected annual loss for a population of 24K.
Beyond physical exposure, Cassia County has a low social vulnerability rating (how susceptible the population is to harm) and a low community resilience rating (its capacity to prepare for and recover from disasters). Both measures sit toward the lower end, indicating relatively modest population sensitivity.
The county's disaster history tells the same story: Cassia County has received 5 federal disaster declarations since 1964, including 2 for biological events and 2 for flood events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 44 Idaho counties, Cassia County ranks #19 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Wildfire | Medium | 0.01 / yr | $4M |
| Winter Weather | Medium | 15.31 / yr | $259K |
| Earthquake | Low | 0.01 / yr | $1M |
| Lightning | Medium | 28.38 / yr | $547K |
| Avalanche | Very Low | 0.01 / yr | $1K |
| Heat Wave | Low | 2.49 / yr | $572K |
| Riverine Flood | Low | 0.75 / yr | $8M |
| Landslide | Very Low | 0.85 / yr | $1K |
| Volcanic Activity | Very Low | 0.00 / yr | $12 |
| Cold Wave | Low | 0.39 / yr | $823K |
| Drought | Very Low | 64.26 / yr | $15K |
| Strong Wind | Low | 0.51 / yr | $244K |
| Ice Storm | Very Low | 0.01 / yr | $9K |
| Hail | Very Low | 0.30 / yr | $40K |
| Tornado | Very Low | 0.22 / yr | $70K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Cassia County has received 5 federal disaster declarations since 1964, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Flood (2), Hurricane (1).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| April 2017 | Flood | Severe Winter Storms and Flooding |
| September 2005 | Hurricane | Hurricane Katrina |
| December 1964 | Flood | Heavy Rains & Flooding |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Cassia County?
Cassia County has a composite FEMA National Risk Index score of 43.6 out of 100, placing it in the Low category and the 44th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Cassia County?
The three highest-rated hazards are Wildfire (Medium, $4M EAL), Winter Weather (Medium, $259K EAL), Earthquake (Low, $1M EAL). These account for most of the county's expected annual losses.
How does Cassia County compare to other Idaho counties?
Cassia County ranks #19 of 44 Idaho counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Cassia County had?
FEMA records 5 federal disaster declarations for Cassia County since 1964, most often 2 for biological events and 2 for flood events. The most recent was Covid-19 Pandemic, declared in April 2020.
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. Cassia County's $16M EAL is a statistical average, not a guarantee for any specific year or address.