Treasure County, Montana
Shrink-swell clay limits houses without basements on 44% of Treasure County's mapped land, a higher share than 89% of US counties and the 6th highest of 53 Montana counties. A shallow water table limits basements on 4%.
8.1% 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. 54% of homes were built before 1980, against 50% nationally; the median home dates from 1972.
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 Treasure County
| Expansive clay (limits slab homes) | 44.2% |
| High water table (limits basements) | 3.8% |
| Septic fields very limited | 81.2% |
| Clay swell (LEP, by area) | 4.9% |
| High-swell land (LEP 6%+) | 44.8% |
| Mapped soil | 606,326 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Midway | 17% | n/a |
| Bainville | 14% | n/a |
| Havre | 6% | n/a |
| McRae | 5% | n/a |
| Lismas | 5% | n/a |
| Pierre | 5% | n/a |
How we count · survey areas MT103 (2025-08-29)
What the numbers mean here
Clay swell averages a linear extensibility of 4.9% by land area here, and 45% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 44% of the mapped land.
Clay shrinks as it dries: 8.1% of the county is in drought on the latest map, and 44% of Treasure County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 15.44 in, 0.34 in above the 1991-2020 average year of 15.10 in.
USDA rates 81% of the land very limited for septic absorption fields.
Drought
8.1% 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 20 weeks, most recently on the September 29, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 36.4% |
| D1 moderate drought or worse | 8.1% |
| 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 Treasure County since 2016.
Rain
| Average year, 1991-2020 | 15.10 in |
| 12 months to August 2026 | 15.44 in (+0.34) |
| 2025 | 19.26 in (+4.16) |
| Wettest year since 1895 | 2011: 21.66 in |
| Driest year since 1895 | 1952: 6.70 in |
| Days with 1 inch or more, normal at HYSHAM (5 mi away) | 1.6 |
Homes
| Housing units | 460 |
| Median year built | 1972 |
| Built before 1980 | 54% |
| Built 2000 or later | 22% |
| Owner-occupied | 68% |
| Median value, owner-occupied | $230,300 |
| Single-family detached | 79% |
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 |
|---|---|---|---|
| Rosebud County, MT | 29 mi | 25% | under 1% |
| Yellowstone County, MT | 52 mi | 23% | 3% |
| Big Horn County, MT | 58 mi | 30% | 1% |
| Musselshell County, MT | 59 mi | 24% | 1% |
| Garfield County, MT | 73 mi | 22% | under 1% |
| Petroleum County, MT | 78 mi | 57% | under 1% |
| Custer County, MT | 82 mi | 19% | 1% |
| Golden Valley County, MT | 91 mi | 26% | 2% |
Sources: USDA SSURGO (August 29, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status