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Walla Walla County, Washington
USDA's soil survey flags shrink-swell clay on 0% of Walla Walla County's mapped land and a shallow water table under basements on 4%, both below the national shares of 15% and 29%. 100% of the county is in drought on the October 13, 2026 Drought Monitor map.
FEMA's flood data list 38 flood losses here since 2016, 24% of them in buildings with basements. 60% of homes were built before 1980, against 50% nationally; the median home dates from 1973.
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 Walla Walla County
| Expansive clay (limits slab homes) | 0.0% |
| High water table (limits basements) | 4.0% |
| Septic fields very limited | 78.7% |
| Clay swell (LEP, by area) | 1.7% |
| High-swell land (LEP 6%+) | 0.0% |
| Mapped soil | 806,516 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Ritzville | 34% | n/a |
| Walla Walla | 17% | n/a |
| Quincy | 6% | n/a |
| Ellisforde | 5% | n/a |
| Adkins | 5% | n/a |
| Athena | 4% | n/a |
How we count · survey areas WA671 (2025-08-28)
What the numbers mean here
Rain over the 12 months to August 2026: 14.40 in, 0.58 in below the 1991-2020 average year of 14.98 in.
USDA rates 79% of the land very limited for septic absorption fields.
With shrink-swell clay on 0% and a shallow water table on 4% of the land, the soil survey points to neither problem across most of Walla Walla County; conditions still vary lot by lot.
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 41 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 | 64.8% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
38 flood losses since 2016, $1.1 million paid. The worst year was 2020, with 28. Foundations of the buildings, where recorded: 24% basements, 10% slabs, 52% crawl spaces, 14% elevated. Median water depth outside the building: 9 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 2 |
| 2018 | 0 |
| 2019 | 3 |
| 2020 | 28 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 14.98 in |
| 12 months to August 2026 | 14.40 in (-0.58) |
| 2025 | 14.06 in (-0.92) |
| Wettest year since 1895 | 1996: 23.03 in |
| Driest year since 1895 | 1935: 9.63 in |
| Days with 1 inch or more, normal at WALLA WALLA RGNL AP (14 mi away) | 1.2 |
Homes
| Housing units | 25,422 |
| Median year built | 1973 |
| Built before 1980 | 60% |
| Built 2000 or later | 23% |
| Owner-occupied | 65% |
| Median value, owner-occupied | $408,900 |
| Single-family detached | 66% |
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 |
|---|---|---|---|
| Columbia County, WA | 28 mi | under 1% | 4% |
| Franklin County, WA | 28 mi | 0% | under 1% |
| Garfield County, WA | 47 mi | 13% | 2% |
| Umatilla County, OR | 47 mi | 7% | 3% |
| Benton County, WA | 50 mi | 0% | 1% |
| Adams County, WA | 53 mi | under 1% | 2% |
| Asotin County, WA | 60 mi | 29% | 5% |
| Whitman County, WA | 64 mi | 1% | 15% |
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