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Glenn County, California

Shrink-swell clay limits houses without basements on 38% of Glenn County's mapped land, a higher share than 86% of US counties and the 7th highest of 54 California counties. A shallow water table limits basements on 15%.

None 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. 54% of homes were built before 1980, against 50% nationally; the median home dates from 1977.

Data as of October 13, 2026 · sources

38%

expansive clay: shrink-swell limits slab homes

15%

high water table: limits basements

0%

in drought, October 13, 2026

54%

of homes built before 1980

Soil under Glenn County

Expansive clay (limits slab homes)37.7%
High water table (limits basements)14.9%
Septic fields very limited79.7%
Clay swell (LEP, by area)5.0%
High-swell land (LEP 6%+)33.4%
Mapped soil866,353 acres
Soil seriesShare hereSeries nationally: expansive clay
Sheetiron9%n/a
Maymen6%n/a
Millsholm6%n/a
Tehama4%n/a
Hillgate4%n/a
Sehorn3%n/a
Colusa County: 55%Tehama County: 15%Lake County: 8%Butte County: 31%Sutter County: 41%Mendocino County: 9%Yuba County: 21%Yolo County: 44%Glenn County ColusaTehamaLakeButteSutterMendocinoYubaYoloGlenn
Glenn 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 CA021 (2025-09-03), CA612 (2025-09-05)

What the numbers mean here

Clay swell averages a linear extensibility of 5.0% by land area here, and 33% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 38% of the mapped land.

Rain over the 12 months to August 2026: 29.23 in, 1.87 in above the 1991-2020 average year of 27.36 in.

USDA rates 80% of the land very limited for septic absorption fields.

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 worse100%
D1 moderate drought or worse0%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

20 flood losses since 2016, $784,498 paid. The worst year was 2017, with 11.

YearFlood losses
20160
201711
20180
20192
20200
20210
20220
20233
20242
20251
2026 to date1

Rain

Average year, 1991-202027.36 in
12 months to August 202629.23 in (+1.87)
202522.87 in (-4.49)
Wettest year since 18951983: 62.28 in
Driest year since 18952020: 7.22 in
Days with 1 inch or more, normal at STONY GORGE RSVR (7 mi away)5.6

Homes

Housing units11,073
Median year built1977
Built before 198054%
Built 2000 or later20%
Owner-occupied61%
Median value, owner-occupied$352,400
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 31 mi 55% 37%
Tehama County, CA 37 mi 15% 3%
Lake County, CA 39 mi 8% 1%
Butte County, CA 43 mi 31% 27%
Sutter County, CA 54 mi 41% 37%
Mendocino County, CA 56 mi 9% 6%
Yuba County, CA 61 mi 21% 5%
Yolo County, CA 69 mi 44% 23%

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