Lewis County, Idaho
A shallow water table limits basements on 33% of Lewis County's mapped land, a higher share than 52% of US counties and the 3rd highest of 43 Idaho counties. Shrink-swell clay limits houses without basements on 23%.
100% 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 1965.
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 Lewis County
| Expansive clay (limits slab homes) | 22.6% |
| High water table (limits basements) | 33.2% |
| Septic fields very limited | 99.5% |
| Clay swell (LEP, by area) | 7.0% |
| High-swell land (LEP 6%+) | 40.3% |
| Mapped soil | 305,401 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Uhlorn | 15% | n/a |
| Nez Perce | 11% | n/a |
| Klickson | 5% | n/a |
| Kettenbach | 5% | n/a |
| Joel | 5% | n/a |
| Southwick | 5% | n/a |
How we count · survey areas ID611 (2025-08-27)
What the numbers mean here
Clay swell averages a linear extensibility of 7.0% by land area here, and 40% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 23% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 23% of Lewis County's mapped land has shrink-swell clay.
On 33% of Lewis County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 26.50 in, 1.58 in above the 1991-2020 average year of 24.92 in.
USDA rates over 99% of the land very limited for septic absorption fields.
Drought
100% 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 52 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 | 100% |
| D2 severe or worse | 74.3% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Lewis County since 2016.
Rain
| Average year, 1991-2020 | 24.92 in |
| 12 months to August 2026 | 26.50 in (+1.58) |
| 2025 | 23.70 in (-1.22) |
| Wettest year since 1895 | 1927: 36.67 in |
| Driest year since 1895 | 1935: 17.05 in |
| Days with 1 inch or more, normal at NEZPERCE (9 mi away) | 0.5 |
Homes
| Housing units | 1,826 |
| Median year built | 1965 |
| Built before 1980 | 74% |
| Built 2000 or later | 10% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $225,300 |
| 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 |
|---|---|---|---|
| Nez Perce County, ID | 17 mi | 7% | 15% |
| Asotin County, WA | 39 mi | 29% | 5% |
| Latah County, ID | 43 mi | 5% | 43% |
| Clearwater County, ID | 47 mi | 1% | 14% |
| Idaho County, ID | 53 mi | 9% | 12% |
| Garfield County, WA | 55 mi | 13% | 2% |
| Wallowa County, OR | 58 mi | 31% | 11% |
| Benewah County, ID | 69 mi | 1% | 40% |
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