102 flood insurance claims·$431,717 paid·3 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 Lewis and Clark County, Montana. 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.
Flash flooding from summer thunderstorms and general flooding events dominate the historical flood profile in Lewis and Clark County, supported by 21 flash flood and 18 general flood events recorded over the last 30 years by the NOAA Storm Events Database. Recent weather impacts include an upper-level trough that triggered thunderstorms and flash flooding over the Horse Gulch burn scar on September 11, 2024, as well as multiple rounds of heavy rain and thunderstorms in June 2023. Additionally, unseasonably warm temperatures and rain in April 2023 caused deep snowpack melt over frozen ground, driving significant runoff.
National Flood Insurance Program records show claims distributed across multiple zones, with 26 claims in Zone A averaging an average 1 inch of recorded water depth and $5,157 payouts. Properties in Zone X recorded 22 claims with an average 2 inches of water and $4,371 payouts, while Zone X_SHADED recorded 22 claims with an average 2 inches of water and $6,302 payouts. Unknown zones accounted for 16 claims averaging an average 2 inches of water and $5,967 payouts, and Zone X_UNSHADED recorded 15 claims with an average 7 inches of recorded water depth and $5,879 payouts. Homeowners and real estate agents in Zone A and moderate-risk zones should pay close attention to these historical claim patterns and localized burn scar vulnerabilities.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
59% of Lewis and Clark County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
63 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 3 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 2018, with 38 claims and $175,800 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.
15 NOAA storm reports from Lewis and Clark County describe what happened, in the words of the forecasters who covered it. Read the Montana flood stories →
16 federal disaster declarations since 1975, 3 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Horse Gulch Fire | Jul 9, 2024 |
| North Hills Fire | Jul 26, 2019 |
| Flooding | May 1, 2018 |
| Alice Creek Fire | Sep 8, 2017 |
| Corral Fire | Jun 25, 2012 |
| Severe Storms And Flooding | Apr 4, 2011 |
| Country Club Fire | Sep 16, 2007 |
| Hurricane Katrina Evacuation | Aug 29, 2005 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
39 since 1996: 21 flash floods and 18 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flash Flood | Sep 11, 2024 | — |
| Flash Flood | Jun 10, 2023 | — |
| Flood | Apr 9, 2023 | $100,000 |
| Flood | Jun 8, 2023 | — |
| Flash Flood | Jul 3, 2022 | — |
| Flash Flood | Jul 3, 2022 | $700,000 |
| Flood | Jun 30, 2020 | — |
| Flood | May 26, 2019 | — |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flash Flood · Sep 11, 2024. An upper level trough passed across the Northern Rockies September 11, which allowed for numerous thunderstorms to develop in the afternoon. Thermodynamic and kinematic ingredients were sufficient for a few strong thunderstorms, mostly across Southwest Montana. Additionally, a series of thunderstorms moved across the Horse Gulch burn scar, which resulted in flash flooding.
Flash Flood · Jun 10, 2023. Several rounds of rain and thunderstorms affected much of Montana during the first half of June. Flash flooding occurred across portions of the region, especially across Fergus County as well as the Rocky Mountains. Fergus County was hit exceptionally hard as several days of occasional heavy rain exasperated area creeks and streams. Casino Creek, located south of Lewistown, was washed out in at least two locations…
Flood · Apr 9, 2023. Unseasonably warm temperatures occurred in the first two weeks of April, with highs near 80 degrees occurring at times. These warm temps, along with occasional rain, resulted in melting of a deep snowpack on top of frozen ground which led to significant runoff into area waterways. Moderate to major flooding occurred along portions of the Milk River and its tributaries. Impactful snowmelt flooding also occurred acr…
Flood · Jun 8, 2023. Several rounds of rain and thunderstorms affected much of Montana during the first half of June. Flash flooding occurred across portions of the region, especially across Fergus County as well as the Rocky Mountains. Fergus County was hit exceptionally hard as several days of occasional heavy rain exasperated area creeks and streams. Casino Creek, located south of Lewistown, was washed out in at least two locations…
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 Lewis and Clark 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.