Custer County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
LowComposite Risk Score
National percentile: 52th
Custer County faces low composite natural disaster risk (NRI Risk Index score 52.4, 52th national percentile), driven primarily by landslide and avalanche exposure. Expected annual loss across all 18 hazard types is $11M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Custer County is low, with a National Risk Index score of 52.4 out of 100 — placing it in the 52nd 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.
Risk here concentrates in landslide (downhill movement of rock, soil, and debris on unstable slopes) at High risk — $414K in expected annual loss and about 7.27 events per year; avalanche (fast-moving snow and debris sliding down steep mountain slopes) at Very High risk — $3M in expected annual loss and about 0.23 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at Low risk — $544K in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $11M in expected annual loss for a population of 4K.
Beyond physical exposure, Custer County has a very high social vulnerability rating (how susceptible the population is to harm) and a very low community resilience rating (its capacity to prepare for and recover from disasters). That combination — a more vulnerable population with limited resilience — can amplify the human cost of any given event.
The county's disaster history tells the same story: Custer County has received 7 federal disaster declarations since 1983, including 2 for biological events and 1 for flood events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 44 Idaho counties, Custer County ranks #13 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Landslide | High | 7.27 / yr | $414K |
| Avalanche | Very High | 0.23 / yr | $3M |
| Wildfire | Low | 0.00 / yr | $544K |
| Earthquake | Low | 0.03 / yr | $951K |
| Riverine Flood | Low | 0.57 / yr | $5M |
| Winter Weather | Low | 20.28 / yr | $40K |
| Lightning | Low | 28.35 / yr | $115K |
| Cold Wave | Low | 0.84 / yr | $266K |
| Volcanic Activity | Very Low | 0.00 / yr | $1 |
| Heat Wave | Very Low | 0.30 / yr | $40K |
| Strong Wind | Very Low | 0.25 / yr | $82K |
| Drought | Very Low | 93.94 / yr | $387 |
| Ice Storm | Very Low | 0.01 / yr | $2K |
| Tornado | Very Low | 0.13 / yr | $4K |
| Hail | Very Low | 0.08 / yr | $2K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Custer County has received 7 federal disaster declarations since 1983, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Flood (1), Hurricane (1).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| August 2017 | Flood | Flooding, Landslides, and Mudslides |
| September 2005 | Hurricane | Hurricane Katrina |
| September 2000 | Fire | Wildfires |
| June 1997 | Severe Storm | Severe Storms, Snowmelt, Land/Mud Slides, Flooding |
| November 1983 | Earthquake | Earthquake |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Custer County?
Custer County has a composite FEMA National Risk Index score of 52.4 out of 100, placing it in the Low category and the 52th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Custer County?
The three highest-rated hazards are Landslide (High, $414K EAL), Avalanche (Very High, $3M EAL), Wildfire (Low, $544K EAL). These account for most of the county's expected annual losses.
How does Custer County compare to other Idaho counties?
Custer County ranks #13 of 44 Idaho counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Custer County had?
FEMA records 7 federal disaster declarations for Custer County since 1983, most often 2 for biological events and 1 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. Custer County's $11M EAL is a statistical average, not a guarantee for any specific year or address.