Wibaux County, Montana
Shrink-swell clay limits houses without basements on 22% of Wibaux County's mapped land, a higher share than 73% of US counties. A shallow water table limits basements on 2%.
The soil survey maps 87% of the county's land area; these shares describe the mapped part. 100% 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. 64% of homes were built before 1980, against 50% nationally; the median home dates from 1973.
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 Wibaux County
| Expansive clay (limits slab homes) | 22.2% |
| High water table (limits basements) | 2.4% |
| Septic fields very limited | 81.4% |
| Clay swell (LEP, by area) | 4.5% |
| High-swell land (LEP 6%+) | 22.2% |
| Mapped soil | 497,025 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Bainville | 17% | n/a |
| Chama | 15% | n/a |
| Flasher | 6% | n/a |
| Regent | 5% | n/a |
| Midway | 3% | n/a |
| Vebar | 3% | n/a |
How we count · survey areas MT109 (2025-08-29)
What the numbers mean here
Clay swell averages a linear extensibility of 4.5% by land area here, and 22% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 22% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 22% of Wibaux County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 13.29 in, 2.48 in below the 1991-2020 average year of 15.77 in.
USDA rates 81% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 25 of the last 52 weeks; the most was 100% of its area, in 18 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 100% |
| D3 extreme or worse | 15.1% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Wibaux County since 2016.
Rain
| Average year, 1991-2020 | 15.77 in |
| 12 months to August 2026 | 13.29 in (-2.48) |
| 2025 | 18.00 in (+2.23) |
| Wettest year since 1895 | 2019: 22.52 in |
| Driest year since 1895 | 1934: 6.04 in |
| Days with 1 inch or more, normal at WIBAUX 2 E (6 mi away) | 2.6 |
Homes
| Housing units | 595 |
| Median year built | 1973 |
| Built before 1980 | 64% |
| Built 2000 or later | 18% |
| Owner-occupied | 73% |
| Median value, owner-occupied | $98,600 |
| Single-family detached | 74% |
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 |
|---|---|---|---|
| Golden Valley County, ND | 20 mi | 7% | 3% |
| Dawson County, MT | 36 mi | 8% | 1% |
| Billings County, ND | 43 mi | 25% | 4% |
| Fallon County, MT | 45 mi | 21% | 1% |
| Slope County, ND | 53 mi | 23% | 6% |
| Richland County, MT | 58 mi | 8% | 2% |
| Prairie County, MT | 59 mi | 10% | 1% |
| McKenzie County, ND | 68 mi | 16% | 4% |
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