Idaho inland flooding risk
Ada County has the highest inland flooding risk in Idaho, scoring 89.8 out of 100 — rated "Relatively Moderate" by FEMA's National Risk Index. Recorded inland flooding events across Idaho have decreased 36% over the past five years compared to the prior five-year period.
| # | County | NRI score | Rating |
NOAA events 2016–2026 |
|---|---|---|---|---|
| 1 | Ada County | 89.8 | Relatively Moderate | 11 |
| 2 | Bonner County | 87 | Relatively Moderate | 7 |
| 3 | Kootenai County | 86.3 | Relatively Moderate | 7 |
| 4 | Canyon County | 80.3 | Relatively Moderate | 6 |
| 5 | Bonneville County | 78.6 | Relatively Moderate | 15 |
| 6 | Shoshone County | 76 | Relatively Moderate | 10 |
| 7 | Idaho County | 72.9 | Relatively Low | 9 |
| 8 | Blaine County | 70.5 | Relatively Low | 16 |
| 9 | Lemhi County | 59.8 | Relatively Low | 8 |
| 10 | Bingham County | 58.8 | Relatively Low | 5 |
| 11 | Owyhee County | 58.7 | Relatively Low | 2 |
| 12 | Madison County | 57.8 | Relatively Low | 10 |
| 13 | Nez Perce County | 57.7 | Relatively Low | 14 |
| 14 | Custer County | 57.3 | Relatively Low | 11 |
| 15 | Valley County | 55.8 | Relatively Low | 1 |
| 16 | Clearwater County | 55.7 | Relatively Low | 3 |
| 17 | Cassia County | 52.7 | Relatively Low | 8 |
| 18 | Bannock County | 51.9 | Relatively Low | 13 |
| 19 | Twin Falls County | 51.1 | Relatively Low | 1 |
| 20 | Latah County | 50.4 | Relatively Low | 17 |
| 21 | Benewah County | 46.9 | Relatively Low | 6 |
| 22 | Boundary County | 45.8 | Relatively Low | 3 |
| 23 | Boise County | 42.9 | Relatively Low | 6 |
| 24 | Fremont County | 41.4 | Relatively Low | 6 |
| 25 | Washington County | 38.2 | Relatively Low | 5 |
| 26 | Jefferson County | 37.1 | Relatively Low | 7 |
| 27 | Adams County | 35.9 | Relatively Low | 1 |
| 28 | Gem County | 35.7 | Relatively Low | 3 |
| 29 | Payette County | 33.9 | Very Low | 1 |
| 30 | Minidoka County | 32.1 | Very Low | 4 |
| 31 | Jerome County | 31.1 | Very Low | 2 |
| 32 | Elmore County | 30.1 | Very Low | 4 |
| 33 | Teton County | 28 | Very Low | 5 |
| 34 | Gooding County | 25.9 | Very Low | 4 |
| 35 | Franklin County | 17.4 | Very Low | 6 |
| 36 | Lincoln County | 14.4 | Very Low | 3 |
| 37 | Lewis County | 12 | Very Low | 3 |
| 38 | Caribou County | 10.7 | Very Low | 6 |
| 39 | Butte County | 9.1 | Very Low | 8 |
| 40 | Power County | 7.6 | Very Low | 12 |
| 41 | Bear Lake County | 7.2 | Very Low | 6 |
| 42 | Oneida County | 4.9 | Very Low | 6 |
| 43 | Camas County | 3.4 | Very Low | 1 |
| 44 | Clark County | 2.1 | Very Low | 5 |
Source: FEMA National Risk Index v1.20.0, December 2025. Scores are 0–100 percentile rankings among all US counties. See the methodology page for definitions. Download the full CSV for all counties.
Inland Flooding risk nationally:
Other hazard risks in Idaho:
Frequently asked questions
What is the highest inland flooding risk county in Idaho?
Ada County, ID has the highest inland flooding risk in Idaho, with a FEMA National Risk Index score of 89.8 out of 100 (rated "Relatively Moderate").
What causes inland flooding risk in Idaho?
Inland flooding covers riverine and surface (pluvial) flooding — the most common and costly natural disaster type in the US. High scores appear across river floodplains in the Midwest, South, and Mid-Atlantic, where legacy development in flood-prone areas and aging stormwater infrastructure concentrate risk.