Valley County, Idaho
USDA's soil survey flags shrink-swell clay on 1% of Valley County's mapped land and a shallow water table under basements on 14%, both below the national shares of 15% and 29%. The soil survey maps 20% of the county's land area; these shares describe the mapped part.
1.9% 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. 34% of homes were built before 1980, against 50% nationally; the median home dates from 1992.
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 Valley County
| Expansive clay (limits slab homes) | 1.0% |
| High water table (limits basements) | 14.1% |
| Septic fields very limited | 85.8% |
| Clay swell (LEP, by area) | 1.6% |
| High-swell land (LEP 6%+) | 1.3% |
| Mapped soil | 475,939 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Pyle | 11% | n/a |
| Koppes | 9% | n/a |
| Bryan | 9% | n/a |
| Archabal | 5% | n/a |
| Shellrock | 5% | n/a |
| Quartzburg | 4% | n/a |
How we count · survey areas ID652 (2025-08-27), ID662 (2025-08-27)
What the numbers mean here
Rain over the 12 months to August 2026: 35.57 in, 0.61 in above the 1991-2020 average year of 34.96 in.
USDA rates 86% of the land very limited for septic absorption fields.
With shrink-swell clay on 1% and a shallow water table on 14% of the land, the soil survey points to neither problem across most of Valley County; conditions still vary lot by lot.
Drought
1.9% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 40 of the last 52 weeks; the most was 100% of its area, on the June 23, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 51.4% |
| D1 moderate drought or worse | 1.9% |
| 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 Valley County since 2016.
Rain
| Average year, 1991-2020 | 34.96 in |
| 12 months to August 2026 | 35.57 in (+0.61) |
| 2025 | 37.13 in (+2.17) |
| Wettest year since 1895 | 1996: 54.84 in |
| Driest year since 1895 | 1935: 21.30 in |
| Days with 1 inch or more, normal at MCCALL (24 mi away) | 1.2 |
Homes
| Housing units | 12,878 |
| Median year built | 1992 |
| Built before 1980 | 34% |
| Built 2000 or later | 35% |
| Owner-occupied | 82% |
| Median value, owner-occupied | $657,000 |
| Single-family detached | 82% |
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 |
|---|---|---|---|
| Adams County, ID | 41 mi | 9% | 7% |
| Boise County, ID | 60 mi | 3% | 2% |
| Washington County, ID | 64 mi | 33% | 3% |
| Gem County, ID | 67 mi | 19% | 9% |
| Idaho County, ID | 69 mi | 9% | 12% |
| Custer County, ID | 78 mi | 3% | 7% |
| Payette County, ID | 81 mi | 4% | 9% |
| Lemhi County, ID | 85 mi | 10% | 12% |
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