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Humboldt County, California

A shallow water table limits basements on 19% of Humboldt County's mapped land and the 10th highest of 54 California counties. Shrink-swell clay limits houses without basements on 10%.

The soil survey maps 90% of the county's land area; these shares describe the mapped part. 1.4% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 20 flood losses here since 2016. 60% of homes were built before 1980, against 50% nationally; the median home dates from 1973.

Data as of October 13, 2026 · sources

10%

expansive clay: shrink-swell limits slab homes

19%

high water table: limits basements

1%

in drought, October 13, 2026

60%

of homes built before 1980

Soil under Humboldt County

Expansive clay (limits slab homes)9.5%
High water table (limits basements)19.1%
Septic fields very limited95.2%
Clay swell (LEP, by area)3.0%
High-swell land (LEP 6%+)8.3%
Mapped soil2,046,330 acres
Soil seriesShare hereSeries nationally: high water table
Sproulish8%n/a
Canoecreek6%n/a
Tannin3%n/a
Yorknorth3%n/a
Coppercreek3%n/a
Redwoodhouse3%n/a
Trinity County: no dataDel Norte County: no dataMendocino County: 6%Siskiyou County: 11%Tehama County: 3%Shasta County: 4%Glenn County: 15%Josephine County: 4%Humboldt County TrinityDel NorteMendocinoSiskiyouTehamaShastaGlennJosephineHumboldt
Humboldt County (heavy outline) and nearby counties, shaded by high water table share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas CA600 (2025-09-05), CA601 (2025-09-03), CA605 (2025-09-03), CA796 (2025-09-03)

What the numbers mean here

On 19% of Humboldt 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: 54.94 in, 6.75 in below the 1991-2020 average year of 61.69 in.

USDA rates 95% of the land very limited for septic absorption fields.

Drought

1.4% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 20 of the last 52 weeks; the most was 85% of its area, in 4 weeks, most recently on the September 15, 2026 map.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse100%
D1 moderate drought or worse1.4%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

20 flood losses since 2016, $885,806 paid. The worst year was 2019, with 5.

YearFlood losses
20161
20172
20180
20195
20200
20211
20221
20231
20244
20253
2026 to date2

Rain

Average year, 1991-202061.69 in
12 months to August 202654.94 in (-6.75)
202568.00 in (+6.31)
Wettest year since 18951983: 108.86 in
Driest year since 18952013: 21.30 in
Days with 1 inch or more, normal at EUREKA WFO WOODLEY ISLAND (14 mi away)9.4

Homes

Housing units62,883
Median year built1973
Built before 198060%
Built 2000 or later16%
Owner-occupied56%
Median value, owner-occupied$446,900
Single-family detached69%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Basement waterproofing, US $3,000 to $10,000 Fixr, February 6, 2026
Sump pump installation, US $800 to $2,000 Fixr, January 31, 2025
Crawl space encapsulation, US $2,000 to $8,000 Fixr, August 29, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Trinity County, CA 43 mi n/a n/a
Del Norte County, CA 72 mi n/a n/a
Mendocino County, CA 92 mi 9% 6%
Siskiyou County, CA 95 mi 11% 11%
Tehama County, CA 98 mi 15% 3%
Shasta County, CA 99 mi 9% 4%
Glenn County, CA 111 mi 38% 15%
Josephine County, OR 118 mi 14% 4%

Sources: USDA SSURGO (September 5, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status