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Lake County, California

USDA's soil survey flags shrink-swell clay on 8% of Lake County's mapped land and a shallow water table under basements on 1%, both below the national shares of 15% and 29%. None of the county is in drought on the October 13, 2026 Drought Monitor map.

FEMA's flood data list 171 flood losses here since 2016, 1% of them in buildings with basements. 51% of homes were built before 1980, against 50% nationally; the median home dates from 1980.

Data as of October 13, 2026 · sources

8%

expansive clay: shrink-swell limits slab homes

1%

high water table: limits basements

0%

in drought, October 13, 2026

51%

of homes built before 1980

Soil under Lake County

Expansive clay (limits slab homes)8.4%
High water table (limits basements)1.0%
Septic fields very limited75.6%
Clay swell (LEP, by area)3.3%
High-swell land (LEP 6%+)9.5%
Mapped soil858,094 acres
Soil seriesShare hereSeries nationally: expansive clay
Maymen11%n/a
Etsel6%n/a
Neuns4%n/a
Sanhedrin4%n/a
Speaker4%n/a
Millsholm3%n/a
Colusa County: 55%Glenn County: 38%Sonoma County: 22%Mendocino County: 9%Napa County: 14%Yolo County: 44%Sutter County: 41%Butte County: 31%Lake County ColusaGlennSonomaMendocinoNapaYoloSutterButteLake
Lake 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 CA033 (2025-09-03)

What the numbers mean here

Rain over the 12 months to August 2026: 40.82 in, 5.20 in below the 1991-2020 average year of 46.02 in.

USDA rates 76% of the land very limited for septic absorption fields.

With shrink-swell clay on 8% and a shallow water table on 1% of the land, the soil survey points to neither problem across most of Lake County; conditions still vary lot by lot.

Drought

0% of the county is in drought (D1 or worse) on the October 13, 2026 map. No part of the county was in drought in the last 52 weeks.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse95.3%
D1 moderate drought or worse0%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

171 flood losses since 2016, $2.6 million paid. The worst year was 2017, with 115. Foundations of the buildings, where recorded: 1% basements, 26% slabs, 45% crawl spaces, 28% elevated. Median water depth outside the building: 12 in.

YearFlood losses
20165
2017115
20180
201933
20202
20212
20221
20236
20245
20252
2026 to date0

Rain

Average year, 1991-202046.02 in
12 months to August 202640.82 in (-5.20)
202540.89 in (-5.13)
Wettest year since 18951983: 97.70 in
Driest year since 18952013: 12.35 in
Days with 1 inch or more, normal at POTTER VALLEY POWERHOUSE (27 mi away)14.5

Homes

Housing units34,400
Median year built1980
Built before 198051%
Built 2000 or later21%
Owner-occupied72%
Median value, owner-occupied$324,300
Single-family detached70%

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
Colusa County, CA 28 mi 55% 37%
Glenn County, CA 39 mi 38% 15%
Sonoma County, CA 42 mi 22% 5%
Mendocino County, CA 43 mi 9% 6%
Napa County, CA 47 mi 14% 6%
Yolo County, CA 54 mi 44% 23%
Sutter County, CA 56 mi 41% 37%
Butte County, CA 72 mi 31% 27%

Sources: USDA SSURGO (September 3, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status