Blaine County, Montana
Shrink-swell clay limits houses without basements on 44% of Blaine County's mapped land, a higher share than 89% of US counties and the 7th highest of 53 Montana counties. A shallow water table limits basements on 2%.
None of the county is in drought on the October 13, 2026 Drought Monitor map, after 21% a week earlier. FEMA's flood data list 1 flood losses here since 2016. 71% 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 Blaine County
| Expansive clay (limits slab homes) | 44.0% |
| High water table (limits basements) | 2.2% |
| Septic fields very limited | 79.4% |
| Clay swell (LEP, by area) | 5.3% |
| High-swell land (LEP 6%+) | 43.4% |
| Mapped soil | 2,733,781 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Phillips | 8% | n/a |
| Telstad | 6% | n/a |
| Elloam | 6% | n/a |
| Hillon | 5% | n/a |
| Kevin | 5% | n/a |
| Vida | 5% | n/a |
How we count · survey areas MT608 (2025-08-30)
What the numbers mean here
Clay swell averages a linear extensibility of 5.3% by land area here, and 43% 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.
Rain over the 12 months to August 2026: 13.26 in, 1.13 in below the 1991-2020 average year of 14.39 in.
USDA rates 79% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 51 of the last 52 weeks; the most was 100% of its area, in 23 weeks, most recently on the May 26, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 87.9% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
1 flood losses since 2016, $5,292 paid. The worst year was 2018, with 1.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 1 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 14.39 in |
| 12 months to August 2026 | 13.26 in (-1.13) |
| 2025 | 14.59 in (+0.20) |
| Wettest year since 1895 | 2016: 22.47 in |
| Driest year since 1895 | 1910: 8.38 in |
| Days with 1 inch or more, normal at CHINOOK (16 mi away) | 1.5 |
Homes
| Housing units | 2,823 |
| Median year built | 1972 |
| Built before 1980 | 71% |
| Built 2000 or later | 12% |
| Owner-occupied | 66% |
| Median value, owner-occupied | $155,500 |
| 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 |
|---|---|---|---|
| Phillips County, MT | 49 mi | 64% | 2% |
| Hill County, MT | 54 mi | 29% | 3% |
| Chouteau County, MT | 77 mi | 39% | 2% |
| Fergus County, MT | 84 mi | 51% | 3% |
| Liberty County, MT | 95 mi | 34% | 3% |
| Petroleum County, MT | 95 mi | 57% | under 1% |
| Valley County, MT | 106 mi | 51% | 2% |
| Judith Basin County, MT | 115 mi | 37% | 4% |
Sources: USDA SSURGO (August 30, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status