HomeWashingtonLewis County
Lewis County, Washington
A shallow water table limits basements on 20% of Lewis County's mapped land. Shrink-swell clay limits houses without basements on 7%.
The soil survey maps 79% of the county's land area; these shares describe the mapped part. None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 116 flood losses here since 2016, 11% of them in buildings with basements. 50% of homes were built before 1980, against 50% nationally; the median home dates from 1980.
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) | 7.3% |
| High water table (limits basements) | 20.2% |
| Septic fields very limited | 87.8% |
| Clay swell (LEP, by area) | 2.8% |
| High-swell land (LEP 6%+) | 7.3% |
| Mapped soil | 1,219,178 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Buckpeak | 6% | n/a |
| Melbourne | 6% | n/a |
| Pheeney | 5% | n/a |
| Cinebar | 5% | n/a |
| Salkum | 5% | n/a |
| Prather | 4% | n/a |
How we count · survey areas WA641 (2025-08-28), WA754 (2025-08-28)
What the numbers mean here
On 20% 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: 74.51 in, 1.36 in above the 1991-2020 average year of 73.15 in.
USDA rates 88% of the land very limited for septic absorption fields.
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 18 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the December 2, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 66.4% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
116 flood losses since 2016, $5.5 million paid. The worst year was 2022, with 88. Foundations of the buildings, where recorded: 11% basements, 28% slabs, 39% crawl spaces, 22% elevated. Median water depth outside the building: 16 in.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 1 |
| 2018 | 1 |
| 2019 | 1 |
| 2020 | 2 |
| 2021 | 3 |
| 2022 | 88 |
| 2023 | 1 |
| 2024 | 0 |
| 2025 | 18 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 73.15 in |
| 12 months to August 2026 | 74.51 in (+1.36) |
| 2025 | 68.55 in (-4.60) |
| Wettest year since 1895 | 1996: 101.63 in |
| Driest year since 1895 | 1952: 44.37 in |
| Days with 1 inch or more, normal at MAYFIELD PWR PLT (12 mi away) | 9.8 |
Homes
| Housing units | 36,512 |
| Median year built | 1980 |
| Built before 1980 | 50% |
| Built 2000 or later | 23% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $385,800 |
| 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 |
|---|---|---|---|
| Cowlitz County, WA | 30 mi | 4% | 10% |
| Thurston County, WA | 33 mi | 3% | 34% |
| Pierce County, WA | 34 mi | 2% | 34% |
| Skamania County, WA | 43 mi | 4% | 5% |
| Wahkiakum County, WA | 52 mi | 4% | 10% |
| Columbia County, OR | 55 mi | 7% | 35% |
| Clark County, WA | 56 mi | 3% | 22% |
| Mason County, WA | 65 mi | under 1% | 45% |
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