Prairie County, Montana
USDA's soil survey flags shrink-swell clay on 10% of Prairie County's mapped land and a shallow water table under basements on 1%, both below the national shares of 15% and 29%. 67.5% 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. 76% of homes were built before 1980, against 50% nationally; the median home dates from 1957.
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 Prairie County
| Expansive clay (limits slab homes) | 10.2% |
| High water table (limits basements) | 0.9% |
| Septic fields very limited | 70.6% |
| Clay swell (LEP, by area) | 3.2% |
| High-swell land (LEP 6%+) | 9.3% |
| Mapped soil | 1,114,300 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Lonna | 20% | n/a |
| Cambeth | 11% | n/a |
| Cabbart | 10% | under 1% |
| Yamacall | 4% | n/a |
| Busby | 3% | n/a |
| Floweree | 3% | n/a |
How we count · survey areas MT079 (2025-08-29)
What the numbers mean here
Rain over the 12 months to August 2026: 11.76 in, 2.17 in below the 1991-2020 average year of 13.93 in.
USDA rates 71% of the land very limited for septic absorption fields.
With shrink-swell clay on 10% and a shallow water table on 1% of the land, the soil survey points to neither problem across most of Prairie County; conditions still vary lot by lot.
Drought
67.5% 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 13 weeks, most recently on the August 11, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 94.5% |
| D1 moderate drought or worse | 67.5% |
| D2 severe or worse | 52.6% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Prairie County since 2016.
Rain
| Average year, 1991-2020 | 13.93 in |
| 12 months to August 2026 | 11.76 in (-2.17) |
| 2025 | 14.89 in (+0.96) |
| Wettest year since 1895 | 2011: 20.16 in |
| Driest year since 1895 | 1934: 4.97 in |
| Days with 1 inch or more, normal at TERRY (10 mi away) | 1.6 |
Homes
| Housing units | 687 |
| Median year built | 1957 |
| Built before 1980 | 76% |
| Built 2000 or later | 12% |
| Owner-occupied | 84% |
| Median value, owner-occupied | $165,700 |
| Single-family detached | 88% |
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 |
|---|---|---|---|
| Custer County, MT | 37 mi | 19% | 1% |
| Dawson County, MT | 42 mi | 8% | 1% |
| McCone County, MT | 58 mi | 12% | under 1% |
| Wibaux County, MT | 59 mi | 22% | 2% |
| Fallon County, MT | 62 mi | 21% | 1% |
| Rosebud County, MT | 71 mi | 25% | under 1% |
| Garfield County, MT | 77 mi | 22% | under 1% |
| Golden Valley County, ND | 79 mi | 7% | 3% |
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