Silver Bow County, Montana
USDA's soil survey flags shrink-swell clay on 2% of Silver Bow County's mapped land and a shallow water table under basements on 5%, both below the national shares of 15% and 29%. None 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. 74% of homes were built before 1980, against 50% nationally; the median home dates from 1956.
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 Silver Bow County
| Expansive clay (limits slab homes) | 2.4% |
| High water table (limits basements) | 5.1% |
| Septic fields very limited | 81.0% |
| Clay swell (LEP, by area) | 2.6% |
| High-swell land (LEP 6%+) | 3.2% |
| Mapped soil | 460,200 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Stecum | 3% | n/a |
| Philipsburg | 3% | n/a |
| Varney | 2% | n/a |
| Valleyflat | 2% | n/a |
| Sebud | 2% | n/a |
| Rubick | 2% | n/a |
How we count · survey areas MT605 (2025-08-29), MT627 (2025-08-31), MT635 (2025-08-31), MT670 (2025-09-03)
What the numbers mean here
Rain over the 12 months to August 2026: 17.24 in, 0.86 in below the 1991-2020 average year of 18.10 in.
USDA rates 81% of the land very limited for septic absorption fields.
With shrink-swell clay on 2% and a shallow water table on 5% of the land, the soil survey points to neither problem across most of Silver Bow County; conditions still vary lot by lot.
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 46 of the last 52 weeks; the most was 100% of its area, in 22 weeks, most recently on the August 25, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| 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 Silver Bow County since 2016.
Rain
| Average year, 1991-2020 | 18.10 in |
| 12 months to August 2026 | 17.24 in (-0.86) |
| 2025 | 18.04 in (-0.06) |
| Wettest year since 1895 | 1975: 28.36 in |
| Driest year since 1895 | 1935: 11.04 in |
| Days with 1 inch or more, normal at BUTTE BERT MOONEY AP (9 mi away) | 0.4 |
Homes
| Housing units | 17,499 |
| Median year built | 1956 |
| Built before 1980 | 74% |
| Built 2000 or later | 13% |
| Owner-occupied | 71% |
| Median value, owner-occupied | $255,200 |
| Single-family detached | 72% |
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 |
|---|---|---|---|
| Deer Lodge County, MT | 27 mi | 6% | 10% |
| Jefferson County, MT | 33 mi | 1% | 7% |
| Granite County, MT | 50 mi | 6% | 7% |
| Madison County, MT | 53 mi | 3% | 4% |
| Beaverhead County, MT | 54 mi | 6% | 9% |
| Broadwater County, MT | 63 mi | 1% | 3% |
| Powell County, MT | 67 mi | 10% | 6% |
| Ravalli County, MT | 71 mi | under 1% | 8% |
Sources: USDA SSURGO (September 3, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status