Flathead County, Montana
USDA's soil survey flags shrink-swell clay on 1% of Flathead County's mapped land and a shallow water table under basements on 3%, both below the national shares of 15% and 29%. None of the county is in drought on the October 13, 2026 Drought Monitor map.
FEMA's flood data list 12 flood losses here since 2016. 36% of homes were built before 1980, against 50% nationally; the median home dates from 1991.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Flathead County
| Expansive clay (limits slab homes) | 0.6% |
| High water table (limits basements) | 3.3% |
| Septic fields very limited | 79.0% |
| Clay swell (LEP, by area) | 1.9% |
| High-swell land (LEP 6%+) | 0.6% |
| Mapped soil | 3,228,390 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Winkler | 3% | n/a |
| Bigarm | 3% | n/a |
| Nooney | 3% | n/a |
| Mitten | 2% | n/a |
| Piegan | 2% | n/a |
| Courville | 1% | n/a |
How we count · survey areas MT603 (2025-09-02), MT617 (2025-08-30), MT619 (2025-08-30), MT629 (2025-08-30), MT633 (2025-08-30), MT651 (2025-09-03)
What the numbers mean here
Rain over the 12 months to August 2026: 42.13 in, 6.27 in above the 1991-2020 average year of 35.86 in.
USDA rates 79% of the land very limited for septic absorption fields.
With shrink-swell clay on 1% and a shallow water table on 3% of the land, the soil survey points to neither problem across most of Flathead County; conditions still vary lot by lot.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 26 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the December 2, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 2.4% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
12 flood losses since 2016, $34,721 paid. The worst year was 2017, with 4.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 4 |
| 2018 | 3 |
| 2019 | 0 |
| 2020 | 1 |
| 2021 | 1 |
| 2022 | 1 |
| 2023 | 1 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 35.86 in |
| 12 months to August 2026 | 42.13 in (+6.27) |
| 2025 | 39.10 in (+3.24) |
| Wettest year since 1895 | 1897: 58.36 in |
| Driest year since 1895 | 1952: 24.81 in |
| Days with 1 inch or more, normal at HUNGRY HORSE DAM (4 mi away) | 3.7 |
Homes
| Housing units | 51,680 |
| Median year built | 1991 |
| Built before 1980 | 36% |
| Built 2000 or later | 36% |
| Owner-occupied | 72% |
| Median value, owner-occupied | $535,500 |
| Single-family detached | 72% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Lake County, MT | 45 mi | 2% | 3% |
| Glacier County, MT | 56 mi | 22% | 2% |
| Sanders County, MT | 64 mi | 2% | 3% |
| Lincoln County, MT | 67 mi | n/a | n/a |
| Pondera County, MT | 84 mi | 35% | 4% |
| Missoula County, MT | 88 mi | 1% | 3% |
| Teton County, MT | 88 mi | 23% | 8% |
| Mineral County, MT | 94 mi | under 1% | 4% |
Sources: USDA SSURGO (September 3, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status