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Sierra County, California

USDA's soil survey flags shrink-swell clay on 5% of Sierra County's mapped land and a shallow water table under basements on 9%, both below the national shares of 15% and 29%. The soil survey maps 27% of the county's land area; these shares describe the mapped part.

22.1% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 7 flood losses here since 2016. 60% of homes were built before 1980, against 50% nationally; the median home dates from 1971.

Data as of October 13, 2026 · sources

5%

expansive clay: shrink-swell limits slab homes

9%

high water table: limits basements

22%

in drought, October 13, 2026

60%

of homes built before 1980

Soil under Sierra County

Expansive clay (limits slab homes)5.1%
High water table (limits basements)8.7%
Septic fields very limited79.1%
Clay swell (LEP, by area)3.2%
High-swell land (LEP 6%+)9.6%
Mapped soil165,355 acres
Soil seriesShare hereSeries nationally: expansive clay
Galeppi5%n/a
Beckwourth5%n/a
Loyalton4%n/a
Balman4%n/a
Calpine4%n/a
Ramelli3%n/a
Nevada County: 2%Plumas County: 4%Placer County: 7%Yuba County: 21%Carson City: 11%Storey County: 30%El Dorado County: 1%Butte County: 31%Sierra County NevadaPlumasPlacerYubaCarson CityStoreyEl DoradoButteSierra
Sierra 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 CA614 (2025-09-03), CA713 (2025-09-03)

What the numbers mean here

Rain over the 12 months to August 2026: 43.71 in, 2.09 in below the 1991-2020 average year of 45.80 in.

USDA rates 79% of the land very limited for septic absorption fields.

With shrink-swell clay on 5% and a shallow water table on 9% of the land, the soil survey points to neither problem across most of Sierra County; conditions still vary lot by lot.

Drought

22.1% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 18 of the last 52 weeks; the most was 90.4% 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 worse22.1%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

7 flood losses since 2016, $117,932 paid. The worst year was 2017, with 7.

YearFlood losses
20160
20177
20180
20190
20200
20210
20220
20230
20240
20250
2026 to date0

Rain

Average year, 1991-202045.80 in
12 months to August 202643.71 in (-2.09)
202547.98 in (+2.18)
Wettest year since 18951983: 86.57 in
Driest year since 18952013: 13.57 in
Days with 1 inch or more, normal at PORTOLA (16 mi away)5.5

Homes

Housing units2,120
Median year built1971
Built before 198060%
Built 2000 or later13%
Owner-occupied72%
Median value, owner-occupied$331,900
Single-family detached93%

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
Nevada County, CA 22 mi 2% 1%
Plumas County, CA 33 mi 4% 2%
Placer County, CA 37 mi 7% 4%
Yuba County, CA 49 mi 21% 5%
Carson City, NV 51 mi 11% 5%
Storey County, NV 54 mi 30% under 1%
El Dorado County, CA 55 mi 1% 2%
Butte County, CA 58 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