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Twin Falls County, Idaho

USDA's soil survey flags shrink-swell clay on 13% of Twin Falls County's mapped land and a shallow water table under basements on 1%, both below the national shares of 15% and 29%. 100% of the county is in drought on the October 13, 2026 Drought Monitor map.

FEMA's flood data list 5 flood losses here since 2016. 49% of homes were built before 1980, against 50% nationally; the median home dates from 1982.

Data as of October 13, 2026 · sources

13%

expansive clay: shrink-swell limits slab homes

1%

high water table: limits basements

100%

in drought, October 13, 2026

49%

of homes built before 1980

Soil under Twin Falls County

Expansive clay (limits slab homes)12.9%
High water table (limits basements)1.2%
Septic fields very limited94.5%
Clay swell (LEP, by area)3.7%
High-swell land (LEP 6%+)19.5%
Mapped soil1,161,600 acres
Soil seriesShare hereSeries nationally: expansive clay
Portneuf10%n/a
Chuska8%n/a
Sluka7%n/a
Roseworth6%n/a
Minveno5%n/a
Chiara4%n/a
Jerome County: 0%Gooding County: 26%Lincoln County: 16%Cassia County: 3%Minidoka County: 1%Owyhee County: 27%Camas County: 19%Blaine County: 11%Twin Falls County JeromeGoodingLincolnCassiaMinidokaOwyheeCamasBlaineTwin Falls
Twin Falls 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 ID704 (2025-08-27)

What the numbers mean here

Rain over the 12 months to August 2026: 8.78 in, 3.77 in below the 1991-2020 average year of 12.55 in.

USDA rates 94% of the land very limited for septic absorption fields.

With shrink-swell clay on 13% and a shallow water table on 1% of the land, the soil survey points to neither problem across most of Twin Falls County; conditions still vary lot by lot.

Drought

100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 52 weeks, most recently on the October 13, 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 worse100%
D2 severe or worse100%
D3 extreme or worse100%
D4 exceptional55.7%

Flood losses since 2016

5 flood losses since 2016, $10,384 paid. The worst year was 2024, with 2.

YearFlood losses
20160
20172
20180
20190
20200
20211
20220
20230
20242
20250
2026 to date0

Rain

Average year, 1991-202012.55 in
12 months to August 20268.78 in (-3.77)
20259.38 in (-3.17)
Wettest year since 18951907: 21.83 in
Driest year since 18951933: 6.48 in
Days with 1 inch or more, normal at JEROME (27 mi away)0.4

Homes

Housing units36,429
Median year built1982
Built before 198049%
Built 2000 or later32%
Owner-occupied71%
Median value, owner-occupied$337,900
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
Jerome County, ID 31 mi under 1% under 1%
Gooding County, ID 44 mi 26% under 1%
Lincoln County, ID 51 mi 16% 1%
Cassia County, ID 53 mi 3% 2%
Minidoka County, ID 63 mi 1% 7%
Owyhee County, ID 79 mi 27% 2%
Camas County, ID 80 mi 19% 22%
Blaine County, ID 80 mi 11% 4%

Sources: USDA SSURGO (August 27, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status