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Siskiyou County, California

USDA's soil survey flags shrink-swell clay on 11% of Siskiyou County's mapped land and a shallow water table under basements on 11%, both below the national shares of 15% and 29%. The soil survey maps 35% of the county's land area; these shares describe the mapped part.

89.9% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 1 flood losses here since 2016. 58% of homes were built before 1980, against 50% nationally; the median home dates from 1976.

Data as of October 13, 2026 · sources

11%

expansive clay: shrink-swell limits slab homes

11%

high water table: limits basements

90%

in drought, October 13, 2026

58%

of homes built before 1980

Soil under Siskiyou County

Expansive clay (limits slab homes)10.9%
High water table (limits basements)11.2%
Septic fields very limited77.8%
Clay swell (LEP, by area)3.2%
High-swell land (LEP 6%+)10.9%
Mapped soil1,385,032 acres
Soil seriesShare hereSeries nationally: expansive clay
Duzel4%n/a
Capjac3%n/a
Jilson3%n/a
Kindig3%n/a
Lassen3%n/a
Pinehurst2%n/a
Jackson County: 31%Shasta County: 9%Trinity County: no dataDel Norte County: no dataJosephine County: 14%Klamath County: 20%Modoc County: 27%Humboldt County: 10%Siskiyou County JacksonShastaTrinityDel NorteJosephineKlamathModocHumboldtSiskiyou
Siskiyou County (heavy outline) and nearby counties, shaded by expansive clay share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas CA602 (2025-09-03), CA604 (2025-09-03), CA684 (2025-09-05)

What the numbers mean here

Rain over the 12 months to August 2026: 30.96 in, 6.75 in below the 1991-2020 average year of 37.71 in.

USDA rates 78% of the land very limited for septic absorption fields.

With shrink-swell clay on 11% and a shallow water table on 11% of the land, the soil survey points to neither problem across most of Siskiyou County; conditions still vary lot by lot.

Drought

89.9% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 28 of the last 52 weeks; the most was 90.2% of its area, in 3 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 worse89.9%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

1 flood losses since 2016, $5,808 paid. The worst year was 2017, with 1.

YearFlood losses
20160
20171
20180
20190
20200
20210
20220
20230
20240
20250
2026 to date0

Rain

Average year, 1991-202037.71 in
12 months to August 202630.96 in (-6.75)
202538.10 in (+0.39)
Wettest year since 18951998: 63.95 in
Driest year since 18952013: 16.12 in
Days with 1 inch or more, normal at YREKA (10 mi away)2.9

Homes

Housing units23,088
Median year built1976
Built before 198058%
Built 2000 or later16%
Owner-occupied69%
Median value, owner-occupied$309,500
Single-family detached74%

What repairs cost

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

WorkRangeSource
Foundation repair, US $2,200 to $8,200 Fixr, January 27, 2026
Pier-and-beam repair, US $2,000 to $15,000 Fixr, January 27, 2026
Foundation inspection, US $300 to $600 Fixr, January 31, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Jackson County, OR 57 mi 31% 19%
Shasta County, CA 63 mi 9% 4%
Trinity County, CA 72 mi n/a n/a
Del Norte County, CA 74 mi n/a n/a
Josephine County, OR 77 mi 14% 4%
Klamath County, OR 88 mi 20% 21%
Modoc County, CA 94 mi 27% 15%
Humboldt County, CA 95 mi 10% 19%

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