Mineral County, Montana
USDA's soil survey flags shrink-swell clay on under 1% of Mineral County's mapped land and a shallow water table under basements on 4%, both below the national shares of 15% and 29%. 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. 47% of homes were built before 1980, against 50% nationally; the median home dates from 1983.
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 Mineral County
| Expansive clay (limits slab homes) | 0.2% |
| High water table (limits basements) | 3.6% |
| Septic fields very limited | 87.2% |
| Clay swell (LEP, by area) | 1.2% |
| High-swell land (LEP 6%+) | 0.2% |
| Mapped soil | 761,957 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Krause | 1% | n/a |
| Half Moon | 1% | n/a |
| Entente | under 1% | n/a |
| McCaffery | under 1% | n/a |
| Tally | under 1% | n/a |
| Nemote | under 1% | n/a |
How we count · survey areas MT603 (2025-09-02)
What the numbers mean here
Rain over the 12 months to August 2026: 42.58 in, 4.37 in above the 1991-2020 average year of 38.21 in.
USDA rates 87% of the land very limited for septic absorption fields.
With shrink-swell clay on under 1% and a shallow water table on 4% of the land, the soil survey points to neither problem across most of Mineral 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 34 of the last 52 weeks; the most was 100% of its area, in 8 weeks, most recently on the December 9, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 61.4% |
| 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 Mineral County since 2016.
Rain
| Average year, 1991-2020 | 38.21 in |
| 12 months to August 2026 | 42.58 in (+4.37) |
| 2025 | 39.65 in (+1.44) |
| Wettest year since 1895 | 1927: 55.43 in |
| Driest year since 1895 | 1952: 22.64 in |
| Days with 1 inch or more, normal at SUPERIOR (10 mi away) | 1.1 |
Homes
| Housing units | 2,572 |
| Median year built | 1983 |
| Built before 1980 | 47% |
| Built 2000 or later | 33% |
| Owner-occupied | 81% |
| Median value, owner-occupied | $364,300 |
| Single-family detached | 76% |
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 | 40 mi | under 1% | 4% |
| Clearwater County, ID | 41 mi | 1% | 14% |
| Sanders County, MT | 44 mi | 2% | 3% |
| Missoula County, MT | 56 mi | 1% | 3% |
| Lake County, MT | 59 mi | 2% | 3% |
| Benewah County, ID | 73 mi | 1% | 40% |
| Latah County, ID | 81 mi | 5% | 43% |
| Kootenai County, ID | 83 mi | 2% | 10% |
Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status