Dallam County, Texas
Shrink-swell clay limits houses without basements on 15% of Dallam County's mapped land, a higher share than 64% of US counties. A shallow water table limits basements on 1%.
13.2% of the county is in drought on the October 13, 2026 Drought Monitor map, down from 97% a week earlier. FEMA's flood data list 2 flood losses here since 2016. 54% of homes were built before 1980, against 50% nationally; the median home dates from 1977.
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 Dallam County
| Expansive clay (limits slab homes) | 15.5% |
| High water table (limits basements) | 1.5% |
| Septic fields very limited | 18.0% |
| Clay swell (LEP, by area) | 3.7% |
| High-swell land (LEP 6%+) | 4.8% |
| Mapped soil | 963,488 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Dallam | 32% | n/a |
| Perico | 10% | n/a |
| Sunray | 9% | n/a |
| Conlen | 9% | n/a |
| Gruver | 8% | n/a |
| Sherm | 5% | 95% |
How we count · survey areas TX111 (2025-09-04)
What the numbers mean here
Clay swell averages a linear extensibility of 3.7% by land area here, and 5% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 15% of the mapped land.
Clay shrinks as it dries: 13.2% of the county is in drought on the latest map, and 15% of Dallam County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 9.40 in, 6.67 in below the 1991-2020 average year of 16.07 in.
Drought
13.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 34 of the last 52 weeks; the most was 100% of its area, in 31 weeks, most recently on the September 29, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 13.2% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
2 flood losses since 2016, $884 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 | 16.07 in |
| 12 months to August 2026 | 9.40 in (-6.67) |
| 2025 | 15.72 in (-0.35) |
| Wettest year since 1895 | 1941: 33.20 in |
| Driest year since 1895 | 2011: 8.07 in |
| Days with 1 inch or more, normal at DALHART MUNI AP (19 mi away) | 3.5 |
Homes
| Housing units | 3,052 |
| Median year built | 1977 |
| Built before 1980 | 54% |
| Built 2000 or later | 17% |
| Owner-occupied | 64% |
| Median value, owner-occupied | $151,400 |
| Single-family detached | 74% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Cities in Dallam County
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Hartley County, TX | 31 mi | 14% | 1% |
| Cimarron County, OK | 33 mi | 22% | 2% |
| Sherman County, TX | 39 mi | 40% | 2% |
| Moore County, TX | 50 mi | 46% | 2% |
| Union County, NM | 51 mi | 28% | 1% |
| Oldham County, TX | 61 mi | 20% | 1% |
| Hansford County, TX | 69 mi | 55% | 2% |
| Texas County, OK | 69 mi | 30% | 3% |
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