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Jefferson County, Washington
A shallow water table limits basements on 39% of Jefferson County's mapped land, a higher share than 58% of US counties and the 8th highest of 39 Washington counties. Shrink-swell clay limits houses without basements on 1%.
The soil survey maps 53% of the county's land area; these shares describe the mapped part. 53% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 12 flood losses here since 2016. 38% of homes were built before 1980, against 50% nationally; the median home dates from 1988.
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 Jefferson County
| Expansive clay (limits slab homes) | 0.6% |
| High water table (limits basements) | 39.3% |
| Septic fields very limited | 91.4% |
| Clay swell (LEP, by area) | 2.7% |
| High-swell land (LEP 6%+) | 0.6% |
| Mapped soil | 611,344 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Dimal | 9% | n/a |
| Hoko | 8% | n/a |
| Solleks | 7% | n/a |
| Alderwood | 5% | n/a |
| Klone | 4% | n/a |
| Snahopish | 4% | n/a |
How we count · survey areas WA631 (2025-08-28), WA632 (2025-08-28)
What the numbers mean here
On 39% of Jefferson 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: 100.33 in, 10.23 in below the 1991-2020 average year of 110.56 in.
USDA rates 91% of the land very limited for septic absorption fields.
Drought
53% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 24 of the last 52 weeks; the most was 70.4% of its area, in 9 weeks, most recently on the September 8, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 53% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
12 flood losses since 2016, $131,906 paid. The worst year was 2022, with 5.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 1 |
| 2018 | 1 |
| 2019 | 1 |
| 2020 | 0 |
| 2021 | 1 |
| 2022 | 5 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 1 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 110.56 in |
| 12 months to August 2026 | 100.33 in (-10.23) |
| 2025 | 94.69 in (-15.87) |
| Wettest year since 1895 | 1999: 142.09 in |
| Driest year since 1895 | 1929: 65.67 in |
| Days with 1 inch or more, normal at SEQUIM 2 E (29 mi away) | 0.6 |
Homes
| Housing units | 19,534 |
| Median year built | 1988 |
| Built before 1980 | 38% |
| Built 2000 or later | 29% |
| Owner-occupied | 79% |
| Median value, owner-occupied | $535,000 |
| Single-family detached | 80% |
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 |
|---|---|---|---|
| Clallam County, WA | 27 mi | 1% | 42% |
| Mason County, WA | 35 mi | under 1% | 45% |
| Kitsap County, WA | 42 mi | under 1% | 65% |
| Island County, WA | 46 mi | 0% | 65% |
| Grays Harbor County, WA | 50 mi | 6% | 20% |
| San Juan County, WA | 52 mi | 0% | 47% |
| Thurston County, WA | 68 mi | 3% | 34% |
| Pierce County, WA | 83 mi | 2% | 34% |
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