Ada County, Idaho Natural Disaster Risk
FEMA National Risk Index assessment · ID
MediumComposite Risk Score
National percentile: 88th
Ada County faces medium composite natural disaster risk (NRI Risk Index score 87.8, 88th national percentile), driven primarily by winter weather and wildfire exposure. Expected annual loss across all 18 hazard types is $116M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Ada County is medium, with a National Risk Index score of 87.8 out of 100 — placing it in the 88th national percentile and near the national midpoint 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 winter weather (heavy snow, blizzards, and hazardous winter conditions) at Very High risk — $3M in expected annual loss and about 8.86 events per year; wildfire (uncontrolled fires that spread across wildland and into communities) at High risk — $27M in expected annual loss and about 0.01 events per year; and heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Medium risk — $7M in expected annual loss and about 4.37 events per year. Across all hazards, FEMA estimates $116M in expected annual loss for a population of 495K.
Beyond physical exposure, Ada County has a very low social vulnerability rating (how susceptible the population is to harm) and a very high community resilience rating (its capacity to prepare for and recover from disasters). A less vulnerable population paired with strong resilience helps the community absorb and recover from events.
The county's disaster history tells the same story: Ada County has received 6 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, Ada County ranks #1 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Winter Weather | Very High | 8.86 / yr | $3M |
| Wildfire | High | 0.01 / yr | $27M |
| Heat Wave | Medium | 4.37 / yr | $7M |
| Strong Wind | High | 0.33 / yr | $4M |
| Lightning | High | 19.81 / yr | $2M |
| Riverine Flood | Medium | 0.79 / yr | $63M |
| Earthquake | Low | 0.00 / yr | $7M |
| Ice Storm | Medium | 0.10 / yr | $706K |
| Volcanic Activity | Very Low | 0.00 / yr | $235 |
| Landslide | Low | 0.15 / yr | $9K |
| Hail | Low | 0.24 / yr | $525K |
| Cold Wave | Low | 0.11 / yr | $2M |
| Avalanche | Very Low | 0.01 / yr | $132 |
| Tornado | Low | 0.06 / yr | $686K |
| Drought | Very Low | 14.29 / yr | $783 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Ada County has received 6 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 |
| October 2017 | Flood | Flooding |
| September 2005 | Hurricane | Hurricane Katrina |
| September 2000 | Fire | Wildfires |
| December 1964 | Flood | Heavy Rains & Flooding |
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Ada County?
Ada County has a composite FEMA National Risk Index score of 87.8 out of 100, placing it in the Medium category and the 88th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Ada County?
The three highest-rated hazards are Winter Weather (Very High, $3M EAL), Wildfire (High, $27M EAL), Heat Wave (Medium, $7M EAL). These account for most of the county's expected annual losses.
How does Ada County compare to other Idaho counties?
Ada County ranks #1 of 44 Idaho counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Ada County had?
FEMA records 6 federal disaster declarations for Ada 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. Ada County's $116M EAL is a statistical average, not a guarantee for any specific year or address.