McMullen County, Texas
Shrink-swell clay limits houses without basements on 35% of McMullen County's mapped land, a higher share than 84% of US counties. A shallow water table limits basements on under 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. 45% of homes were built before 1980, against 50% nationally; the median home dates from 1986.
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 McMullen County
| Expansive clay (limits slab homes) | 35.4% |
| High water table (limits basements) | 0.2% |
| Septic fields very limited | 48.1% |
| Clay swell (LEP, by area) | 7.9% |
| High-swell land (LEP 6%+) | 33.5% |
| Mapped soil | 745,101 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Cochina | 7% | n/a |
| Houla | 6% | n/a |
| Montell | 4% | n/a |
| Salco | 4% | n/a |
| Campbellton | 4% | n/a |
| Esseville | 3% | n/a |
How we count · survey areas TX311 (2025-09-04)
What the numbers mean here
Clay swell averages a linear extensibility of 7.9% by land area here, and 33% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 35% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 35% of McMullen County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 19.97 in, 4.70 in below the 1991-2020 average year of 24.67 in.
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 41 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 | 66.6% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in McMullen County since 2016.
Rain
| Average year, 1991-2020 | 24.67 in |
| 12 months to August 2026 | 19.97 in (-4.70) |
| 2025 | 16.21 in (-8.46) |
| Wettest year since 1895 | 1919: 43.15 in |
| Driest year since 1895 | 1917: 7.04 in |
| Days with 1 inch or more, normal at CALLIHAM (15 mi away) | 7.9 |
Homes
| Housing units | 348 |
| Median year built | 1986 |
| Built before 1980 | 45% |
| Built 2000 or later | 30% |
| Owner-occupied | 78% |
| Median value, owner-occupied | $97,100 |
| Single-family detached | 66% |
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 |
|---|---|---|---|
| Live Oak County, TX | 28 mi | 29% | under 1% |
| La Salle County, TX | 32 mi | 35% | under 1% |
| Atascosa County, TX | 35 mi | 34% | under 1% |
| Frio County, TX | 46 mi | 10% | under 1% |
| Duval County, TX | 49 mi | 4% | under 1% |
| Bee County, TX | 51 mi | 25% | 11% |
| Jim Wells County, TX | 54 mi | 27% | 19% |
| Karnes County, TX | 57 mi | 52% | under 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