Harmon County, Oklahoma
Shrink-swell clay limits houses without basements on 25% of Harmon County's mapped land, a higher share than 75% of US counties. A shallow water table limits basements on 2%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 2 flood losses here since 2016. 78% of homes were built before 1980, against 50% nationally; the median home dates from 1964.
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 Harmon County
| Expansive clay (limits slab homes) | 24.7% |
| High water table (limits basements) | 1.6% |
| Septic fields very limited | 81.7% |
| Clay swell (LEP, by area) | 4.1% |
| High-swell land (LEP 6%+) | 23.7% |
| Mapped soil | 343,526 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Westill | 8% | n/a |
| Grandfield | 7% | n/a |
| Woodward | 7% | n/a |
| Aspermont | 6% | n/a |
| Tilvern | 6% | n/a |
| Vernon | 6% | n/a |
How we count · survey areas OK057 (2025-08-29)
What the numbers mean here
Clay swell averages a linear extensibility of 4.1% by land area here, and 24% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 25% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 25% of Harmon County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 14.46 in, 11.07 in below the 1991-2020 average year of 25.53 in.
USDA rates 82% 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 43 of the last 52 weeks; the most was 100% of its area, in 43 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 | 72.5% |
| D4 exceptional | 20.7% |
Flood losses since 2016
2 flood losses since 2016, $80,347 paid. The worst year was 2016, with 2.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 25.53 in |
| 12 months to August 2026 | 14.46 in (-11.07) |
| 2025 | 20.02 in (-5.51) |
| Wettest year since 1895 | 1941: 44.03 in |
| Driest year since 1895 | 1970: 12.69 in |
| Days with 1 inch or more, normal at MANGUM (22 mi away) | 7.6 |
Homes
| Housing units | 1,354 |
| Median year built | 1964 |
| Built before 1980 | 78% |
| Built 2000 or later | 9% |
| Owner-occupied | 70% |
| Median value, owner-occupied | $79,700 |
| Single-family detached | 85% |
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 |
|---|---|---|---|
| Greer County, OK | 21 mi | 26% | 3% |
| Childress County, TX | 26 mi | 12% | 1% |
| Jackson County, OK | 27 mi | 35% | 10% |
| Collingsworth County, TX | 29 mi | 7% | under 1% |
| Hardeman County, TX | 32 mi | 34% | 1% |
| Beckham County, OK | 37 mi | 3% | 2% |
| Hall County, TX | 46 mi | 1% | under 1% |
| Wheeler County, TX | 50 mi | 1% | 2% |
Sources: USDA SSURGO (August 29, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status