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Lewis and Clark County, Montana

USDA's soil survey flags shrink-swell clay on 6% of Lewis and Clark County's mapped land and a shallow water table under basements on 3%, 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 40 flood losses here since 2016. 48% of homes were built before 1980, against 50% nationally; the median home dates from 1982.

Data as of October 13, 2026 · sources

6%

expansive clay: shrink-swell limits slab homes

3%

high water table: limits basements

0%

in drought, October 13, 2026

48%

of homes built before 1980

Soil under Lewis and Clark County

Expansive clay (limits slab homes)6.5%
High water table (limits basements)3.2%
Septic fields very limited82.5%
Clay swell (LEP, by area)2.6%
High-swell land (LEP 6%+)6.6%
Mapped soil2,092,583 acres
Soil seriesShare hereSeries nationally: expansive clay
Reeder4%n/a
Mocmont3%n/a
Tolex3%n/a
Regent3%n/a
Castner3%n/a
Nooney3%n/a
Powell County: 10%Teton County: 23%Cascade County: 35%Broadwater County: 1%Granite County: 6%Jefferson County: 1%Missoula County: 1%Pondera County: 35%Lewis and Clark County PowellTetonCascadeBroadwaterGraniteJeffersonMissoulaPonderaLewis and Clark
Lewis and Clark 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 MT603 (2025-09-02), MT630 (2025-08-30), MT631 (2025-08-30), MT633 (2025-08-30)

What the numbers mean here

Rain over the 12 months to August 2026: 23.83 in, 1.53 in above the 1991-2020 average year of 22.30 in.

USDA rates 83% of the land very limited for septic absorption fields.

With shrink-swell clay on 6% and a shallow water table on 3% of the land, the soil survey points to neither problem across most of Lewis and Clark County; conditions still vary lot by lot.

Drought

0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 36 of the last 52 weeks; the most was 96.1% of its area, in 3 weeks, most recently on the November 4, 2025 map.

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

Flood losses since 2016

40 flood losses since 2016, $178,216 paid. The worst year was 2018, with 38. Median water depth outside the building: 4 in.

YearFlood losses
20160
20170
201838
20191
20200
20210
20220
20230
20241
20250
2026 to date0

Rain

Average year, 1991-202022.30 in
12 months to August 202623.83 in (+1.53)
202522.02 in (-0.28)
Wettest year since 18951975: 37.60 in
Driest year since 18951935: 11.78 in
Days with 1 inch or more, normal at ROGERS PASS 9 NNE (6 mi away)2.1

Homes

Housing units34,082
Median year built1982
Built before 198048%
Built 2000 or later29%
Owner-occupied70%
Median value, owner-occupied$393,500
Single-family detached66%

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
Powell County, MT 32 mi 10% 6%
Teton County, MT 48 mi 23% 8%
Cascade County, MT 51 mi 35% 2%
Broadwater County, MT 69 mi 1% 3%
Granite County, MT 70 mi 6% 7%
Jefferson County, MT 71 mi 1% 7%
Missoula County, MT 71 mi 1% 3%
Pondera County, MT 76 mi 35% 4%

Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status