Boise County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
LowComposite Risk Score
National percentile: 49th
Boise County faces low composite natural disaster risk (NRI Risk Index score 48.9, 49th national percentile), driven primarily by landslide and wildfire exposure. Expected annual loss across all 18 hazard types is $16M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Boise County at low composite risk, with a National Risk Index score of 48.9 out of 100 — placing it in the 49th 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 Boise County's expected losses come from landslide (downhill movement of rock, soil, and debris on unstable slopes) at Medium risk — $356K in expected annual loss and about 2.09 events per year; wildfire (uncontrolled fires that spread across wildland and into communities) at Medium risk — $8M in expected annual loss and about 0.02 events per year; and avalanche (fast-moving snow and debris sliding down steep mountain slopes) at High risk — $1M in expected annual loss and about 0.10 events per year. Across all hazards, FEMA estimates $16M in expected annual loss for a population of 8K.
Beyond physical exposure, Boise County has a low 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.
The federal record bears this out: Boise County has received 7 federal disaster declarations since 1964, including 2 for biological events and 2 for fire events. The most recent was Covid-19 Pandemic (biological), declared in April 2020.
Among 44 Idaho counties, Boise County ranks #15 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Landslide | Medium | 2.09 / yr | $356K |
| Wildfire | Medium | 0.02 / yr | $8M |
| Avalanche | High | 0.10 / yr | $1M |
| Winter Weather | Low | 17.70 / yr | $70K |
| Riverine Flood | Low | 0.82 / yr | $6M |
| Earthquake | Very Low | 0.01 / yr | $158K |
| Volcanic Activity | Very Low | 0.00 / yr | $3 |
| Strong Wind | Low | 0.29 / yr | $225K |
| Heat Wave | Very Low | 1.47 / yr | $36K |
| Ice Storm | Very Low | 0.04 / yr | $8K |
| Drought | Very Low | 7.80 / yr | $1 |
| Lightning | Very Low | 23.22 / yr | $32K |
| Cold Wave | Very Low | 0.05 / yr | $13K |
| Hail | Very Low | 0.20 / yr | $11K |
| Tornado | Very Low | 0.08 / yr | $13K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Boise County has received 7 federal disaster declarations since 1964, most recently Covid-19 Pandemic in April 2020. Most frequent causes: Biological (2), Fire (2), Hurricane (1).
| Declared | Type | Disaster |
|---|---|---|
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2012 | Fire | Karney Fire |
| September 2005 | Hurricane | Hurricane Katrina |
| September 2000 | Fire | Wildfires |
| January 1997 | Severe Storm | Severe Storms, Flooding, Mud and Landslides |
| December 1964 | Flood | Heavy Rains & Flooding |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Boise County?
Boise County has a composite FEMA National Risk Index score of 48.9 out of 100, placing it in the Low category and the 49th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Boise County?
The three highest-rated hazards are Landslide (Medium, $356K EAL), Wildfire (Medium, $8M EAL), Avalanche (High, $1M EAL). These account for most of the county's expected annual losses.
How does Boise County compare to other Idaho counties?
Boise County ranks #15 of 44 Idaho counties for overall natural disaster risk, with a low rating.
How many federally declared disasters has Boise County had?
FEMA records 7 federal disaster declarations for Boise County since 1964, most often 2 for biological events and 2 for fire 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. Boise County's $16M EAL is a statistical average, not a guarantee for any specific year or address.