321
Recorded events
38
Counties affected
2
Direct deaths
$25.5M
Property damage
Idaho flash flood history: 321 recorded events across 38 counties between 1996 and 2025.
Decade by decade
Idaho flash flood history by decade
The 2000s are the busiest decade on record with 120 reported flash flood events across Idaho. Earlier decades are thinner because systematic reporting for this hazard expanded over time, not because the weather was calmer.
County ranking
Counties with the most flash flood events in Idaho
| Rank | County | Events | Deaths | Damage | Span |
|---|---|---|---|---|---|
| #1 | Bannock County | 40 | 0 | $3.0M | 1997–2025 |
| #2 | Power County | 28 | 0 | $36K | 1996–2024 |
| #3 | Cassia County | 22 | 1 | $130K | 1996–2023 |
| #4 | Boise County | 20 | 0 | $100K | 1997–2025 |
| #5 | Owyhee County | 18 | 1 | $0 | 1996–2015 |
| #6 | Lemhi County | 16 | 0 | $275K | 2003–2024 |
| #7 | Oneida County | 14 | 0 | $9K | 1997–2023 |
| #8 | Blaine County | 14 | 0 | $1K | 2007–2021 |
| #9 | Nez Perce County | 14 | 0 | $6.2M | 1998–2023 |
| #10 | Elmore County | 13 | 0 | $100K | 1998–2023 |
| #11 | Idaho County | 12 | 0 | $8.9M | 2002–2025 |
| #12 | Ada County | 10 | 0 | $1.1M | 1997–2025 |
| #13 | Custer County | 10 | 0 | $0 | 1998–2025 |
| #14 | Twin Falls County | 8 | 0 | $0 | 1996–2014 |
| #15 | Latah County | 8 | 0 | $2.2M | 1998–2023 |
| #16 | Fremont County | 7 | 0 | $18K | 2004–2025 |
| #17 | Valley County | 6 | 0 | $10K | 1999–2010 |
| #18 | Bonneville County | 6 | 0 | $802K | 2015–2023 |
| #19 | Madison County | 6 | 0 | $1.1M | 2004–2023 |
| #20 | Bingham County | 5 | 0 | $315K | 2003–2014 |
| #21 | Kootenai County | 5 | 0 | $26K | 1998–2023 |
| #22 | Camas County | 4 | 0 | $0 | 2006–2023 |
| #23 | Washington County | 4 | 0 | $140K | 1998–2011 |
| #24 | Franklin County | 4 | 0 | $25K | 2009–2023 |
| #25 | Butte County | 3 | 0 | $23K | 1998–2014 |
Significant events
Deadliest flash flood events in Idaho
| Date | County | Scale | Deaths | Injuries |
|---|---|---|---|---|
| Jun 7, 2009 | Owyhee County | — | 1 | 0 |
| Jul 29, 1996 | Cassia County | — | 1 | 1 |