Lemhi County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
Very LowComposite Risk Score
National percentile: 41th
Lemhi County faces very low composite natural disaster risk (NRI Risk Index score 41.4, 41th national percentile), driven primarily by landslide and wildfire exposure. Expected annual loss across all 18 hazard types is $11M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Lemhi County carries a very low composite natural disaster risk, with a National Risk Index score of 41.4 out of 100 — placing it in the 41st national percentile and among the lowest-risk counties in the country. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
The county's risk is driven primarily by landslide (downhill movement of rock, soil, and debris on unstable slopes) at Medium risk — $139K in expected annual loss and about 4.10 events per year; wildfire (uncontrolled fires that spread across wildland and into communities) at Medium risk — $2M in expected annual loss and about 0.00 events per year; and lightning (electrical discharges from storms that ignite fires and cause casualties) at Medium risk — $591K in expected annual loss and about 31.11 events per year. Across all hazards, FEMA estimates $11M in expected annual loss for a population of 8K.
Beyond physical exposure, Lemhi County has a medium 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). Both measures sit toward the lower end, indicating relatively modest population sensitivity.
History supports the rating: Lemhi County has received 5 federal disaster declarations since 1984, including 2 for biological events and 1 for hurricane events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 44 Idaho counties, Lemhi County ranks #20 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Landslide | Medium | 4.10 / yr | $139K |
| Wildfire | Medium | 0.00 / yr | $2M |
| Lightning | Medium | 31.11 / yr | $591K |
| Avalanche | Very Low | 0.01 / yr | $1K |
| Riverine Flood | Low | 0.64 / yr | $8M |
| Earthquake | Very Low | 0.02 / yr | $288K |
| Cold Wave | Low | 0.96 / yr | $383K |
| Winter Weather | Very Low | 27.98 / yr | $17K |
| Drought | Very Low | 68.80 / yr | $355 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
| Heat Wave | Very Low | 0.37 / yr | $23K |
| Ice Storm | Very Low | 0.01 / yr | $3K |
| Hail | Very Low | 0.14 / yr | $10K |
| Strong Wind | Very Low | 0.20 / yr | $25K |
| Tornado | Very Low | 0.10 / yr | $7K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Lemhi County has received 5 federal disaster declarations since 1984, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Hurricane (1), Fire (1).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2005 | Hurricane | Hurricane Katrina |
| September 2000 | Fire | Wildfires |
| February 1984 | Snowstorm | Ice Jams and Flooding |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Lemhi County?
Lemhi County has a composite FEMA National Risk Index score of 41.4 out of 100, placing it in the Very Low category and the 41th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Lemhi County?
The three highest-rated hazards are Landslide (Medium, $139K EAL), Wildfire (Medium, $2M EAL), Lightning (Medium, $591K EAL). These account for most of the county's expected annual losses.
How does Lemhi County compare to other Idaho counties?
Lemhi County ranks #20 of 44 Idaho counties for overall natural disaster risk, with a very low rating.
How many federally declared disasters has Lemhi County had?
FEMA records 5 federal disaster declarations for Lemhi County since 1984, most often 2 for biological events and 1 for hurricane 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. Lemhi County's $11M EAL is a statistical average, not a guarantee for any specific year or address.