Adams County, Idaho
USDA's soil survey flags shrink-swell clay on 9% of Adams County's mapped land and a shallow water table under basements on 7%, both below the national shares of 15% and 29%. The soil survey maps 36% of the county's land area; these shares describe the mapped part.
94.2% 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. 42% of homes were built before 1980, against 50% nationally; the median home dates from 1986.
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 Adams County
| Expansive clay (limits slab homes) | 9.4% |
| High water table (limits basements) | 7.3% |
| Septic fields very limited | 98.0% |
| Clay swell (LEP, by area) | 3.3% |
| High-swell land (LEP 6%+) | 8.8% |
| Mapped soil | 314,731 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Riggins | 21% | n/a |
| Meland | 13% | n/a |
| Bluebell | 10% | n/a |
| Rockly | 6% | n/a |
| Ticanot | 4% | n/a |
| Klicker | 3% | n/a |
How we count · survey areas ID652 (2025-08-27), ID656 (2025-08-27)
What the numbers mean here
Rain over the 12 months to August 2026: 29.83 in, 0.72 in below the 1991-2020 average year of 30.55 in.
USDA rates 98% of the land very limited for septic absorption fields.
With shrink-swell clay on 9% and a shallow water table on 7% of the land, the soil survey points to neither problem across most of Adams County; conditions still vary lot by lot.
Drought
94.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 2 weeks, most recently on the June 23, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 94.2% |
| D2 severe or worse | 26.1% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Adams County since 2016.
Rain
| Average year, 1991-2020 | 30.55 in |
| 12 months to August 2026 | 29.83 in (-0.72) |
| 2025 | 31.70 in (+1.15) |
| Wettest year since 1895 | 1940: 48.42 in |
| Driest year since 1895 | 1935: 19.92 in |
| Days with 1 inch or more, normal at MCCALL (17 mi away) | 1.2 |
Homes
| Housing units | 2,674 |
| Median year built | 1986 |
| Built before 1980 | 42% |
| Built 2000 or later | 29% |
| Owner-occupied | 85% |
| Median value, owner-occupied | $376,500 |
| Single-family detached | 92% |
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 |
|---|---|---|---|
| Washington County, ID | 34 mi | 33% | 3% |
| Valley County, ID | 41 mi | 1% | 14% |
| Gem County, ID | 56 mi | 19% | 9% |
| Wallowa County, OR | 61 mi | 31% | 11% |
| Baker County, OR | 62 mi | 47% | 7% |
| Payette County, ID | 62 mi | 4% | 9% |
| Boise County, ID | 72 mi | 3% | 2% |
| Union County, OR | 81 mi | 26% | 21% |
Sources: USDA SSURGO (August 27, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status