Sanders County, Montana
USDA's soil survey flags shrink-swell clay on 2% of Sanders County's mapped land and a shallow water table under basements on 3%, both below the national shares of 15% and 29%. The soil survey maps 81% of the county's land area; these shares describe the mapped part.
0.1% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list no flood losses here since 2016. 37% of homes were built before 1980, against 50% nationally; the median home dates from 1992.
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 Sanders County
| Expansive clay (limits slab homes) | 2.3% |
| High water table (limits basements) | 2.8% |
| Septic fields very limited | 85.4% |
| Clay swell (LEP, by area) | 1.6% |
| High-swell land (LEP 6%+) | 2.8% |
| Mapped soil | 1,438,003 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Bigarm | 7% | n/a |
| Winkler | 6% | n/a |
| Mitten | 4% | n/a |
| Holloway | 3% | n/a |
| Tevis | 2% | n/a |
| Minesinger | 2% | n/a |
How we count · survey areas ID670 (2025-08-27), MT603 (2025-09-02), MT651 (2025-09-03)
What the numbers mean here
Rain over the 12 months to August 2026: 35.86 in, 3.97 in above the 1991-2020 average year of 31.89 in.
USDA rates 85% of the land very limited for septic absorption fields.
With shrink-swell clay on 2% and a shallow water table on 3% of the land, the soil survey points to neither problem across most of Sanders County; conditions still vary lot by lot.
Drought
0.1% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 33 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 | 91.2% |
| D1 moderate drought or worse | 0.1% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Sanders County since 2016.
Rain
| Average year, 1991-2020 | 31.89 in |
| 12 months to August 2026 | 35.86 in (+3.97) |
| 2025 | 33.51 in (+1.62) |
| Wettest year since 1895 | 1996: 45.03 in |
| Driest year since 1895 | 1952: 18.95 in |
| Days with 1 inch or more, normal at LIBBY 32 SSE (14 mi away) | 1.3 |
Homes
| Housing units | 6,808 |
| Median year built | 1992 |
| Built before 1980 | 37% |
| Built 2000 or later | 36% |
| Owner-occupied | 81% |
| Median value, owner-occupied | $359,000 |
| Single-family detached | 78% |
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 |
|---|---|---|---|
| Shoshone County, ID | 43 mi | under 1% | 4% |
| Mineral County, MT | 44 mi | under 1% | 4% |
| Lake County, MT | 52 mi | 2% | 3% |
| Lincoln County, MT | 57 mi | n/a | n/a |
| Flathead County, MT | 64 mi | 1% | 3% |
| Kootenai County, ID | 69 mi | 2% | 10% |
| Benewah County, ID | 77 mi | 1% | 40% |
| Bonner County, ID | 78 mi | under 1% | 14% |
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