Madison County, Montana
USDA's soil survey flags shrink-swell clay on 3% of Madison County's mapped land and a shallow water table under basements on 4%, 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. 33% of homes were built before 1980, against 50% nationally; the median home dates from 1995.
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 Madison County
| Expansive clay (limits slab homes) | 3.1% |
| High water table (limits basements) | 4.4% |
| Septic fields very limited | 71.9% |
| Clay swell (LEP, by area) | 2.4% |
| High-swell land (LEP 6%+) | 3.1% |
| Mapped soil | 2,345,805 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Crago | 4% | n/a |
| Kalsted | 4% | n/a |
| Oro Fino | 4% | n/a |
| Varney | 3% | n/a |
| Musselshell | 3% | n/a |
| Nuley | 2% | n/a |
How we count · survey areas MT605 (2025-08-29), MT623 (2025-08-30), MT635 (2025-08-31), MT636 (2025-08-31)
What the numbers mean here
Rain over the 12 months to August 2026: 21.73 in, 1.25 in below the 1991-2020 average year of 22.98 in.
USDA rates 72% of the land very limited for septic absorption fields.
With shrink-swell clay on 3% and a shallow water table on 4% of the land, the soil survey points to neither problem across most of Madison 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 50 of the last 52 weeks; the most was 100% of its area, in 28 weeks, most recently on the September 22, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 10.9% |
| 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 Madison County since 2016.
Rain
| Average year, 1991-2020 | 22.98 in |
| 12 months to August 2026 | 21.73 in (-1.25) |
| 2025 | 22.98 in (+0.00) |
| Wettest year since 1895 | 1909: 33.63 in |
| Driest year since 1895 | 1934: 16.05 in |
| Days with 1 inch or more, normal at ENNIS (10 mi away) | 0.7 |
Homes
| Housing units | 6,396 |
| Median year built | 1995 |
| Built before 1980 | 33% |
| Built 2000 or later | 41% |
| Owner-occupied | 81% |
| Median value, owner-occupied | $470,100 |
| 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 |
|---|---|---|---|
| Gallatin County, MT | 39 mi | 9% | 9% |
| Beaverhead County, MT | 49 mi | 6% | 9% |
| Silver Bow County, MT | 53 mi | 2% | 5% |
| Jefferson County, MT | 55 mi | 1% | 7% |
| Park County, MT | 68 mi | 11% | 4% |
| Broadwater County, MT | 73 mi | 1% | 3% |
| Clark County, ID | 75 mi | 4% | 4% |
| Deer Lodge County, MT | 79 mi | 6% | 10% |
Sources: USDA SSURGO (August 31, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status