Idaho floods

Every recorded flood since 1996 · 44 counties with a record

NOAA's Storm Events Database records 790 floods and flash floods in Idaho from 1996 through June 30, 2026, about 26 a year since 2000. The deadliest was the July 29, 1996 flash flood in Cassia County: 1 death and 1 injury. Idaho ranks 47th of 52 states and territories by count and 46th of 51 per square mile.

Floods in Idaho, 1996 to 2026

Flood records per year (NOAA Storm Events); 2026 to June 30, 2026.

recorded, no damage figure
under $1 million
$1 million or more
$10 million or more
$100 million or more, or 10 deaths
$1 billion or more, or 100 deaths
a year's colour: its recorded damage or deaths
a year with a death

Records: 7901996 to June 30, 2026
A year since 2000: 26average
Deaths: 35 injuries
Damage, 2025 dollars: $369Mas filed
Busiest year: 2017117 records

Source: NOAA NCEI Storm Events Database, records through June 30, 2026; deaths and damage as filed, damage in 2025 dollars. Search the record at NCEI.

Are floods and flash floods common in Idaho?

Idaho averages about 26 floods and flash floods a year since 2000, 47th of 52 states and territories by count. The busiest year on record was 2017 (117). Per 10,000 square miles of land, Idaho records 96 floods and flash floods since 1996, 46th of 51 states and territories by that measure.

Source: NOAA NCEI Storm Events Database, records since 1996, per 10,000 square miles of land area (Census Bureau 2024 Gazetteer; places under 1,000 square miles not ranked). Damage colours: Storm Events damage, 2025 dollars.

Which counties in Idaho have the most floods and flash floods?

Per square mile, Madison County leads Idaho: 26 days with a flood since 1996, 55.4 per 1,000 square miles of land. By raw count, Bannock County has the most flood records (68 since 1996); large counties collect more records simply by covering more ground, so the ranking counts days with a record per unit of area (a storm filed for several forecast zones adds several records but one day).

Madison County 55.4 (26)
Bannock County 53.0 (68)
Benewah County 37.3 (38)
Latah County 34.4 (52)
Kootenai County 32.3 (56)
Ada County 21.9 (24)
Power County 20.7 (38)
Canyon County 20.4 (13)
Nez Perce County 17.7 (28)
Payette County 17.2 (7)
Jefferson County 16.5 (18)
Teton County 15.6 (7)

Source: NOAA NCEI Storm Events Database, days with a record in the county since 1996 per 1,000 square miles of land (Census Bureau 2024 Gazetteer); in brackets, the count of records.

When is flood season in Idaho?

Idaho's floods and flash floods by month. The busiest month is June (155 records).

The values, month by month

Jan 43 · Feb 64 · Mar 94 · Apr 63 · May 112 · Jun 155 · Jul 88 · Aug 104 · Sep 47 · Oct 2 · Nov 1 · Dec 17 (records).

Source: NOAA NCEI Storm Events Database, records by the month they began, since 1996.

What were the deadliest floods and flash floods in Idaho?

Idaho: the storms with the most deaths since 1996
Date	Record	Killed	Injured	Damage
1996-07-29	Flash FloodMalta, Cassia County Heavy rain produced flash flooding with water 3 to 4 feet deep across the east bound lanes of Interstate 84 near mile marker 261. A driver rounded a corner and drove into the flooded area. The vehicle was forced off the right side of the highway into deeper water in the roadside ditch. The vehicle rolled and was ...	1	1	–
2009-06-06	Flash FloodMurphy, Owyhee County Flash Flooding was reported by law enforcement along Highway 78 and closed a section from Grandview to Walters Ferry, Idaho. A fatality occured when a vehicle was swept into the Snake River near Murphy, Idaho.	1	0	–
2017-05-01	FloodSun Vly, Blaine County One storm episode: 2 records in 2 places; the totals are the episode's. Winter snow melt continued from record winter snowfall and flooding continued throughout much of May in much of southeast Idaho especially in the central mountains and along the Big Wood River.	1	0	$16M

Source: NOAA NCEI Storm Events Database: deaths direct and indirect, as filed by the National Weather Service, summed over each storm (one episode, or one named storm filed by several offices). Storm names from the titles of FEMA declarations that name the storm's counties.

The costliest floods and flash floods in Idaho

Idaho: the most damaging storms since 1993, 2025 dollars
Date	Record	Killed	Injured	Damage
1997-06-01	FloodGooding County and 2 more · forecast zone Western Magic Valley	0	0	$92M
1996-02-08	FloodLemhi County · forecast zone Western Lemhi County	0	1	$83M
2017-02-04	FloodAdelaide, Minidoka County One storm episode: 14 records in 14 places, 2017-02-04 to 2017-02-05; the totals are the episode's.	0	0	$26M
2014-08-05	FloodBarrymore, Jerome County One storm episode: 2 records in 2 places, 2014-08-05 to 2014-08-06; the totals are the episode's.	0	0	$20M
2017-05-01	FloodSun Vly, Blaine County One storm episode: 2 records in 2 places; the totals are the episode's.	1	0	$16M
2017-02-08	FloodJerome County One storm episode: 3 records in 3 places; the totals are the episode's.	0	0	$8.1M
2024-04-14	Flash FloodWinona, Idaho County	0	0	$7.5M
1997-06-01	FloodBonner County and 2 more · forecast zone Northern Panhandle	0	0	$7.4M

Source: NOAA NCEI Storm Events Database: property and crop damage as estimated by the National Weather Service, in 2025 dollars.

Are floods and flash floods becoming more frequent in Idaho?

Idaho's count per decade against the whole country's, and its share. NOAA recorded every event type only from 1996, so earlier decades are not comparable; the share of the national total is the fairer comparison across decades.

Floods: Idaho and the United States by decade (2020s to June 30, 2026)
Decade	Idaho	United States	Idaho's share
1996-99	126	20,986	0.60%
2000s	167	54,913	0.30%
2010s	375	68,322	0.55%
2020-26	122	43,563	0.28%

Source: NOAA NCEI Storm Events Database.

The most recent floods and flash floods in Idaho

The 12 most recent records, to June 30, 2026
Date	Record	Damage
2026-06-26	Flash FloodCaldwell, Canyon County	$7.0M
2026-03-13	FloodMoscow, Latah County	$15K
2026-03-13	FloodAhsahka, Clearwater County	$510K
2026-01-27	FloodTendoy, Lemhi County	–
2025-12-24	FloodSmall, Clark County	$3K
2025-12-10	FloodMc Arthur, Boundary County	$2K
2025-12-10	FloodKingston, Shoshone County	$20K
2025-12-10	FloodClark Fork, Bonner County	$20K
2025-09-11	Flash FloodGrangeville Arp, Idaho County	$10K
2025-09-09	Flash FloodChallis, Custer County	–
2025-08-26	Flash FloodBarber, Ada County	–
2025-08-26	Flash FloodGarden Vly, Boise County	–

Source: NOAA NCEI Storm Events Database, records through June 30, 2026; the newest months are revised by NCEI as reports arrive. Search the record at NCEI.

Federal disaster declarations for floods and flash floods in Idaho

FEMA has declared 25 disasters in Idaho for floods and flash floods, counting its incident type and declarations that name flood in the title (FEMA files most storm disasters under Severe Storm); 25 were major disasters, the latest on June 30, 2026.

The 12 most recent
Declared	Number	Title	Areas named
2026-06-30	DR-4917	Severe Storms, Straight-Line Winds, Flooding, Landslides, and Mudslides	6
2024-06-10	DR-4789	Severe Storm, Flooding, Landslides, and Mudslides	3
2019-06-12	DR-4443	Severe Storms, Flooding, Landslides, and Mudslides	6
2017-10-07	DR-4342	Flooding	2
2017-08-27	DR-4333	Flooding, Landslides, and Mudslides	5
2017-05-18	DR-4313	Severe Storms, Flooding, Landslides, and Mudslides	9
2017-04-21	DR-4310	Severe Winter Storms and Flooding	11
2011-05-20	DR-1987	Flooding, Landslides, and Mudslides	6
2010-07-27	DR-1927	Severe Storms and Flooding	7
2008-07-31	DR-1781	Flooding	2
2006-02-27	DR-1630	Severe Storms and Flooding	1
2005-07-06	DR-1592	Heavy Rains and Flooding	2

Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), through October 2, 2026. OpenFEMA dataset page.