133 flood insurance claims·$498,925 paid·2 federal flood & hurricane disasters
Share of the whole county outline, rivers and lakes included; parts FEMA hasn’t mapped count as zero.
Shaded areas are FEMA’s mapped flood hazard zones in and around Ada County, Idaho. Zoomed out they are simplified; at street level the map switches to FEMA’s exact layer. Tap anywhere to check that spot, or search an address above.
Slow-moving summer thunderstorms and monsoonal moisture patterns drive the flood risk in Ada County, supported by 14 recorded flood events and 10 flash flood events over the last 30 years. Recent historical impacts include heavy rainfall and strong winds in June 2023 that overwhelmed stormwater drainages, flooded downtown and North-End Boise streets, and stranded vehicles. An earlier monsoonal surge in August 2025 brought near-record precipitable water levels and slow-moving, training storms driven by regional terrain.
National Flood Insurance Program records show claims distributed across multiple zones. Zone X accounts for 56 claims with an average payout of $11,712 and an average recorded water depth of 8 inches. Zone A accounts for 52 claims with an average payout of $6,509 and an average recorded water depth of 2 inches. Zone X_UNSHADED records an average payout of $22,041 with an average water depth of 2 inches across 5 claims. Homeowners and real estate agents in Zone X and Zone A should pay the closest attention to these flood risks, as these zones represent the highest concentration of historical insurance claims in the county.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
19% of Ada County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
64 NFIP claims with a recorded rated flood zone, 1978 to date. The zone is the one FEMA used to rate that policy, which may not match today’s map. Source: OpenFEMA NFIP claims.
In flood insurance claims here that reported a flood depth, the average was 5 inches.
Drawn to scale against an 80-inch door. Even a few inches soaks flooring, the bottom of the drywall and anything plugged in near the floor.
Average of the depths reported on claims (zero and implausible values left out); FEMA’s record doesn’t say exactly where each depth was measured. Source: OpenFEMA NFIP claims.
The worst year was 2017, with 37 claims and $267,509 paid, the year of Flooding.
Bar height is scaled by square root so ordinary years stay visible next to the worst one. NFIP claims by year of loss. Source: OpenFEMA.
4 NOAA storm reports from Ada County describe what happened, in the words of the forecasters who covered it. Read the Idaho flood stories →
6 federal disaster declarations since 1964, 2 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Flooding | Mar 29, 2017 |
| Hurricane Katrina | Aug 29, 2005 |
| Wildfires | Jul 27, 2000 |
| Heavy Rains & Flooding | Dec 31, 1964 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
24 since 1996: 10 flash floods and 14 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flash Flood | Aug 26, 2025 | — |
| Flood | Jun 13, 2023 | — |
| Flash Flood | Jun 6, 2023 | $1.0M |
| Flood | Aug 10, 2022 | — |
| Flash Flood | Aug 1, 2021 | — |
| Flash Flood | Apr 30, 2020 | — |
| Flood | Feb 8, 2017 | — |
| Flood | Mar 6, 2017 | — |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flash Flood · Aug 26, 2025. Monsoonal moisture surged into the region over a three day period, the most intense of which was the 26th. High atmospheric moisture content combined with weak flow in a monsoonal pattern to produce very moist storms moving very slowly. Additionally, as terrain served as the main trigger for convection, storms would train over the same spots for much longer than normal. Precipitable water was at near record levels…
Flood · Jun 13, 2023. A nearly stationary upper level low over the Four Corners region brought periods of heavy rain and thunderstorms which caused localized urban flooding in south central Idaho. Rainfall totals were around 0.50 inches, but the previous days rainfall made areas more prone to localized flooding.
Flash Flood · Jun 6, 2023. Thunderstorms developed across southwest Idaho early Tuesday evening and produced |heavy rain and strong winds across portions of the Lower Treasure Valley, including the city of Boise. Social media, weather spotters, and emergency manager reports indicated flooding of many streets in downtown Boise and the North-End Boise area. Water overwhelmed storm water drainages and flowed onto sidewalks and lawns. Water up…
Flood · Aug 10, 2022. An upper level trough on the West Coast slowly edged in between a ridge of high pressure to the east of the region. This allowed for monsoon moisture to move into the region along with strong southwest flow. Several days of isolated supercells occurred, bringing heavy rain and large hail to the region.
National Weather Service narratives, lightly trimmed. Source: NOAA Storm Events Database.
Every colour on the map above is a place on this drawing: where the ground sits relative to the flood FEMA plans for.
If a building in Ada County is in a high-risk zone (A or V) and its mortgage comes from a federally regulated or insured lender, or is federally backed, flood insurance is required.
Outside those zones it is optional, and often worth having: from 2014 to 2024 nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area. Since Risk Rating 2.0, NFIP premiums are set for each building, so the only reliable price is a quote: FloodSmart.gov or a local agent.