Johnson County, Wyoming
Shrink-swell clay limits houses without basements on 18% of Johnson County's mapped land, a higher share than 67% of US counties and the 6th highest of 22 Wyoming counties. A shallow water table limits basements on 1%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list no flood losses here since 2016. 46% of homes were built before 1980, against 50% nationally; the median home dates from 1984.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Johnson County
| Expansive clay (limits slab homes) | 17.6% |
| High water table (limits basements) | 0.9% |
| Septic fields very limited | 69.5% |
| Clay swell (LEP, by area) | 4.0% |
| High-swell land (LEP 6%+) | 18.0% |
| Mapped soil | 2,597,164 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Shingle | 9% | n/a |
| Theedle | 6% | n/a |
| Kishona | 4% | n/a |
| Samday | 4% | n/a |
| Agneston | 3% | n/a |
| Cambria | 2% | n/a |
How we count · survey areas WY619 (2025-09-04), WY650 (2025-09-04), WY719 (2025-09-04)
What the numbers mean here
Clay swell averages a linear extensibility of 4.0% by land area here, and 18% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 18% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 18% of Johnson County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 11.12 in, 4.07 in below the 1991-2020 average year of 15.19 in.
USDA rates 69% of the land very limited for septic absorption fields.
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 45 of the last 52 weeks; the most was 100% of its area, in 35 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 100% |
| D3 extreme or worse | 74.7% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Johnson County since 2016.
Rain
| Average year, 1991-2020 | 15.19 in |
| 12 months to August 2026 | 11.12 in (-4.07) |
| 2025 | 16.55 in (+1.36) |
| Wettest year since 1895 | 1923: 22.60 in |
| Driest year since 1895 | 1960: 9.12 in |
| Days with 1 inch or more, normal at BUFFALO (22 mi away) | 1.5 |
Homes
| Housing units | 4,659 |
| Median year built | 1984 |
| Built before 1980 | 46% |
| Built 2000 or later | 30% |
| Owner-occupied | 82% |
| Median value, owner-occupied | $326,800 |
| Single-family detached | 78% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Sheridan County, WY | 53 mi | 21% | 1% |
| Campbell County, WY | 54 mi | 22% | 1% |
| Washakie County, WY | 55 mi | 5% | 2% |
| Natrona County, WY | 74 mi | 17% | 1% |
| Big Horn County, WY | 77 mi | 12% | 4% |
| Converse County, WY | 91 mi | 16% | 1% |
| Hot Springs County, WY | 95 mi | 17% | 3% |
| Weston County, WY | 101 mi | 27% | 1% |
Sources: USDA SSURGO (September 4, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status