Owyhee County, Idaho
Shrink-swell clay limits houses without basements on 27% of Owyhee County's mapped land, a higher share than 78% of US counties and the 2nd highest of 43 Idaho counties. A shallow water table limits basements on 2%.
The soil survey maps 80% of the county's land area; these shares describe the mapped part. 98.8% 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. 45% of homes were built before 1980, against 50% nationally; the median home dates from 1984.
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 Owyhee County
| Expansive clay (limits slab homes) | 26.9% |
| High water table (limits basements) | 2.1% |
| Septic fields very limited | 91.9% |
| Clay swell (LEP, by area) | 5.1% |
| High-swell land (LEP 6%+) | 30.8% |
| Mapped soil | 3,912,213 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Wickahoney | 6% | n/a |
| Arbidge | 5% | n/a |
| Snowmore | 4% | n/a |
| Bruncan | 4% | n/a |
| Monasterio | 3% | n/a |
| Heckison | 2% | n/a |
How we count · survey areas ID665 (2025-08-27), ID675 (2025-08-27), ID677 (2025-08-28)
What the numbers mean here
Clay swell averages a linear extensibility of 5.1% by land area here, and 31% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 27% of the mapped land.
Clay shrinks as it dries: 98.8% of the county is in drought on the latest map, and 27% of Owyhee County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 9.39 in, 2.91 in below the 1991-2020 average year of 12.30 in.
USDA rates 92% of the land very limited for septic absorption fields.
Drought
98.8% 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 98.8% 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 | 98.8% |
| D2 severe or worse | 93% |
| D3 extreme or worse | 85.8% |
| D4 exceptional | 53.2% |
Flood losses since 2016
FEMA's flood data list no flood losses in Owyhee County since 2016.
Rain
| Average year, 1991-2020 | 12.30 in |
| 12 months to August 2026 | 9.39 in (-2.91) |
| 2025 | 11.23 in (-1.07) |
| Wettest year since 1895 | 1983: 19.67 in |
| Driest year since 1895 | 1966: 6.86 in |
| Days with 1 inch or more, normal at BRUNEAU (29 mi away) | 0.1 |
Homes
| Housing units | 4,869 |
| Median year built | 1984 |
| Built before 1980 | 45% |
| Built 2000 or later | 28% |
| Owner-occupied | 73% |
| Median value, owner-occupied | $359,800 |
| 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 |
|---|---|---|---|
| Ada County, ID | 61 mi | 20% | 4% |
| Elmore County, ID | 67 mi | 7% | 2% |
| Gooding County, ID | 75 mi | 26% | under 1% |
| Canyon County, ID | 77 mi | 1% | 14% |
| Twin Falls County, ID | 79 mi | 13% | 1% |
| Malheur County, OR | 83 mi | 19% | 4% |
| Camas County, ID | 96 mi | 19% | 22% |
| Jerome County, ID | 98 mi | under 1% | under 1% |
Sources: USDA SSURGO (August 28, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status