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Lassen County, California

Shrink-swell clay limits houses without basements on 21% of Lassen County's mapped land, a higher share than 71% of US counties. A shallow water table limits basements on 6%.

58.5% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 22 flood losses here since 2016. 54% of homes were built before 1980, against 50% nationally; the median home dates from 1977.

Data as of October 13, 2026 · sources

21%

expansive clay: shrink-swell limits slab homes

6%

high water table: limits basements

59%

in drought, October 13, 2026

54%

of homes built before 1980

Soil under Lassen County

Expansive clay (limits slab homes)20.8%
High water table (limits basements)5.6%
Septic fields very limited91.0%
Clay swell (LEP, by area)3.9%
High-swell land (LEP 6%+)19.4%
Mapped soil3,970,171 acres
Soil seriesShare hereSeries nationally: expansive clay
Devada4%n/a
Petescreek3%n/a
Ravendale2%n/a
Searles2%n/a
Orhood1%n/a
Longcreek1%n/a
Washoe County: 34%Plumas County: 4%Modoc County: 27%Shasta County: 9%Sierra County: 5%Butte County: 31%Tehama County: 15%Nevada County: 2%Lassen County WashoePlumasModocShastaSierraButteTehamaNevadaLassen
Lassen 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 CA604 (2025-09-03), CA608 (2025-09-03), CA685 (2025-09-05), CA708 (2025-09-03), CA713 (2025-09-03), CA789 (2025-09-03)

What the numbers mean here

Clay swell averages a linear extensibility of 3.9% by land area here, and 19% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 21% of the mapped land.

Clay shrinks as it dries: 58.5% of the county is in drought on the latest map, and 21% of Lassen County's mapped land has shrink-swell clay.

Rain over the 12 months to August 2026: 18.90 in, 0.77 in below the 1991-2020 average year of 19.67 in.

USDA rates 91% of the land very limited for septic absorption fields.

Drought

58.5% 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 92.5% of its area, on the April 7, 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 worse58.5%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

22 flood losses since 2016, $912,024 paid. The worst year was 2017, with 22.

YearFlood losses
20160
201722
20180
20190
20200
20210
20220
20230
20240
20250
2026 to date0

Rain

Average year, 1991-202019.67 in
12 months to August 202618.90 in (-0.77)
202522.84 in (+3.17)
Wettest year since 18951906: 35.06 in
Driest year since 18952013: 8.55 in
Days with 1 inch or more, normal at SUSANVILLE 2SW (20 mi away)2.2

Homes

Housing units12,231
Median year built1977
Built before 198054%
Built 2000 or later16%
Owner-occupied68%
Median value, owner-occupied$265,300
Single-family detached75%

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
Washoe County, NV 50 mi 34% 3%
Plumas County, CA 51 mi 4% 2%
Modoc County, CA 61 mi 27% 15%
Shasta County, CA 75 mi 9% 4%
Sierra County, CA 78 mi 5% 9%
Butte County, CA 89 mi 31% 27%
Tehama County, CA 94 mi 15% 3%
Nevada County, CA 97 mi 2% 1%

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