Ada County, Idaho: Natural Disaster Risk and History
Ada County, Idaho has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 87.8 out of 100, higher than about 87% of US counties, with winter storms, wildfires and heat waves scoring highest of its 18 hazards and $116 million a year in expected losses.
OpenFEMA lists 4 federal disaster declarations that included Ada County since 1964, not counting 2 for COVID-19; the latest is DR-4342-ID (Flooding, declared 7 October 2017). NOAA's Storm Prediction Center recorded 13 tornadoes touching Ada County from 1950 to 2025.
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Population 494,805 Buildings worth $93 billion Area 1,071 sq mi Risk rank in Idaho 1 of 44 FIPS 16001
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Winter weather | Very High | 98.9 | $3.0 million | about 8.9 a year | 168 |
| Wildfire | Relatively High | 98.3 | $27 million | about once every 87 years | — |
| Heat wave | Relatively Moderate | 92.9 | $7.0 million | about 4.4 a year | 42 |
| Strong wind | Relatively High | 91.8 | $3.8 million | about once every 3.0 years | 13 |
| Lightning | Relatively High | 90.1 | $2.0 million | about 2 a year | 187,020 strikes |
| Inland flooding | Relatively Moderate | 89.8 | $63 million | about once every 1.3 years | 22 |
| Earthquake | Relatively Low | 88.2 | $6.6 million | about once every 403 years | — |
| Ice storm | Relatively Moderate | 80.5 | $705,587 | about once every 9.6 years | 7 |
| Volcanic activity | Very Low | 74.3 | $235 | rarer than once in 1,000 years | 2 |
| Landslide | Relatively Low | 69.1 | $8,900 | about once every 6.8 years | — |
| Hail | Relatively Low | 54.5 | $524,766 | about once every 4.1 years | 9.2 |
| Cold wave | Relatively Low | 51.7 | $1.7 million | about once every 9.5 years | 2 |
| Tornado | Relatively Low | 27.0 | $686,018 | about once every 18 years | 8 |
| Avalanche | Very Low | 27.0 | $132 | about once every 100 years | 0 |
| Drought | Very Low | 14.6 | $783 | about 14 a year | 448 |
| Coastal flooding | Not Applicable | — | — | — | — |
| Hurricane | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 4
Most common: Flood 2, Hurricane 1, Fire 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1960s | 1 | Flood |
| 2000s | 2 | Hurricane, Fire |
| 2010s | 1 | Flood |
The last 4
Widest declarations that included Ada County
- Hurricane Katrina (2005, EM-3244-ID): 44 Idaho counties designated.
- Heavy Rains & Flooding (1964, DR-186-ID): 27 Idaho counties designated.
- Wildfires (2000, DR-1341-ID): 15 Idaho counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Idaho also had 8 statewide declarations with no county list.
Tornado record since 1950 13
| Tornadoes touching the county | 13 |
|---|---|
| Strongest-rated | (E)F1 ×3 |
| Peak month | August (5) |
| Deadliest | — |
| Longest path | 2 Jun 1967, F0, 3.8 mi path |
| Most recent | 26 May 2023, EF0, 1 mi path |
| Deaths / injuries on those paths | 0 / 0 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 10 | 3 | 0 | 0 | 0 | 0 | 0 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 2 | 1 | 0 | 2 | 2 | 5 | 0 | 1 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How Ada County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Ada County (this page) | — | Relatively Moderate | 87.8 | Winter weather |
| Canyon County | 42 km | Relatively Low | 71.7 | Winter weather |
| Elmore County | 63 km | Relatively Low | 52.0 | Wildfire |
| Gem County | 69 km | Very Low | 34.4 | Wildfire |
| Boise County | 73 km | Relatively Low | 48.9 | Landslide |
| Payette County | 75 km | Very Low | 17.1 | Wildfire |
Nearest by distance between county centres. Every county in Idaho, ranked.
Vulnerability and resilience
| Social vulnerability | Very Low 10.6 |
|---|---|
| Community resilience | Very High 92.2 |
| Community risk factor | 0.63 |
| Expected annual loss, all hazards | $116 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for Ada County's main hazards
- Right now: National Weather Service alerts for Idaho · all official warnings on Global Incident Tracker.
- Winter weather: Power outages now · Carbon monoxide in winter
- Wildfire: US wildfires now · Wildfire smoke: what protects you
- Heat wave: Heatstroke warning signs
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about Ada County
What natural disasters is Ada County, Idaho most at risk from?
Ada County, Idaho has a Relatively Moderate natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 87.8 out of 100, higher than about 87% of US counties, with winter storms, wildfires and heat waves scoring highest of its 18 hazards and $116 million a year in expected losses.
How many federal disaster declarations has Ada County had?
OpenFEMA lists 4 federal disaster declarations that included Ada County since 1964, not counting 2 for COVID-19; the latest is DR-4342-ID (Flooding, declared 7 October 2017). Another 8 Idaho declarations were made statewide without a county list.
How many tornadoes have hit Ada County?
NOAA's Storm Prediction Center recorded 13 tornadoes touching Ada County from 1950 to 2025.
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.