Missoula County, Montana
USDA's soil survey flags shrink-swell clay on 1% of Missoula 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 39 flood losses here since 2016. 45% of homes were built before 1980, against 50% nationally; the median home dates from 1985.
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 Missoula County
| Expansive clay (limits slab homes) | 1.4% |
| High water table (limits basements) | 3.3% |
| Septic fields very limited | 87.3% |
| Clay swell (LEP, by area) | 1.6% |
| High-swell land (LEP 6%+) | 1.4% |
| Mapped soil | 1,696,370 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Winkler | 11% | n/a |
| Holloway | 7% | n/a |
| Waldbillig | 6% | n/a |
| Repp | 3% | n/a |
| Tevis | 3% | n/a |
| Bigarm | 3% | n/a |
How we count · survey areas MT603 (2025-09-02), MT606 (2025-08-29), MT633 (2025-08-30), MT638 (2025-08-31), MT647 (2025-09-03)
What the numbers mean here
Rain over the 12 months to August 2026: 35.17 in, 5.44 in above the 1991-2020 average year of 29.73 in.
USDA rates 87% 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 Missoula 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 16 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 | 1.1% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
39 flood losses since 2016, $346,744 paid. The worst year was 2018, with 32.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 3 |
| 2018 | 32 |
| 2019 | 2 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 29.73 in |
| 12 months to August 2026 | 35.17 in (+5.44) |
| 2025 | 32.27 in (+2.54) |
| Wettest year since 1895 | 1927: 44.22 in |
| Driest year since 1895 | 1935: 17.05 in |
| Days with 1 inch or more, normal at MISSOULA INTL AP (12 mi away) | 0.2 |
Homes
| Housing units | 56,930 |
| Median year built | 1985 |
| Built before 1980 | 45% |
| Built 2000 or later | 32% |
| Owner-occupied | 59% |
| Median value, owner-occupied | $472,100 |
| Single-family detached | 58% |
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 | 43 mi | 2% | 3% |
| Powell County, MT | 47 mi | 10% | 6% |
| Granite County, MT | 49 mi | 6% | 7% |
| Mineral County, MT | 56 mi | under 1% | 4% |
| Ravalli County, MT | 66 mi | under 1% | 8% |
| Lewis and Clark County, MT | 71 mi | 6% | 3% |
| Deer Lodge County, MT | 74 mi | 6% | 10% |
| Sanders County, MT | 78 mi | 2% | 3% |
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