Grayson County, Texas
Shrink-swell clay limits houses without basements on 60% of Grayson County's mapped land, a higher share than 94% of US counties. A shallow water table limits basements on 4%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 76 flood losses here since 2016, 0% of them in buildings with basements. 44% of homes were built before 1980, against 50% nationally; the median home dates from 1985.
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 Grayson County
| Expansive clay (limits slab homes) | 59.6% |
| High water table (limits basements) | 3.9% |
| Septic fields very limited | 81.5% |
| Clay swell (LEP, by area) | 7.7% |
| High-swell land (LEP 6%+) | 55.4% |
| Urban land, not rated | 1.0% |
| Mapped soil | 626,106 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Normangee | 9% | 72% |
| Crockett | 8% | 94% |
| Wilson | 7% | 88% |
| Vertel | 7% | n/a |
| Fairlie | 7% | 70% |
| Houston Black | 5% | 91% |
How we count · survey areas TX181 (2025-09-04)
What the numbers mean here
Clay swell averages a linear extensibility of 7.7% by land area here, and 55% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 60% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 60% of Grayson County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 34.28 in, 7.11 in below the 1991-2020 average year of 41.39 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 35 of the last 52 weeks; the most was 100% of its area, in 8 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 | 40.4% |
| D3 extreme or worse | 0.7% |
| D4 exceptional | 0% |
Flood losses since 2016
76 flood losses since 2016, $3.0 million paid. The worst year was 2017, with 43. Foundations of the buildings, where recorded: 80% slabs, 17% crawl spaces, 3% elevated. Median water depth outside the building: 10 in.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 43 |
| 2018 | 5 |
| 2019 | 6 |
| 2020 | 3 |
| 2021 | 3 |
| 2022 | 2 |
| 2023 | 2 |
| 2024 | 3 |
| 2025 | 7 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 41.39 in |
| 12 months to August 2026 | 34.28 in (-7.11) |
| 2025 | 40.46 in (-0.93) |
| Wettest year since 1895 | 2015: 73.93 in |
| Driest year since 1895 | 1963: 19.56 in |
| Days with 1 inch or more, normal at SHERMAN (6 mi away) | 14.3 |
Homes
| Housing units | 62,132 |
| Median year built | 1985 |
| Built before 1980 | 44% |
| Built 2000 or later | 32% |
| Owner-occupied | 67% |
| Median value, owner-occupied | $248,400 |
| Single-family detached | 72% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Cities in Grayson County
| City | Expansive clay | High water table | Homes |
|---|---|---|---|
| Bells | 83% | 7% | 934 |
| Collinsville | 40% | 0% | 795 |
| Denison | 41% | 1% | 11,397 |
| Dorchester | 73% | under 1% | 41 |
| Gunter | 84% | 6% | 762 |
| Howe | 77% | 2% | 1,477 |
| Knollwood | 76% | 0% | 418 |
| Pottsboro | 66% | 0% | 1,104 |
| Sadler | 70% | 0% | 120 |
| Sherman | 61% | 3% | 19,846 |
| Southmayd | 82% | 3% | 540 |
| Tioga | 74% | 0% | 590 |
| Tom Bean | 40% | under 1% | 323 |
| Van Alstyne | 78% | under 1% | 2,465 |
| Whitesboro | 56% | 0% | 1,692 |
| Whitewright | 75% | 2% | 859 |
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Marshall County, OK | 28 mi | 30% | 1% |
| Collin County, TX | 30 mi | 72% | 1% |
| Cooke County, TX | 31 mi | 38% | under 1% |
| Fannin County, TX | 33 mi | 66% | 23% |
| Bryan County, OK | 33 mi | 42% | 19% |
| Denton County, TX | 39 mi | 50% | 1% |
| Love County, OK | 40 mi | 17% | 2% |
| Johnston County, OK | 48 mi | 21% | 19% |
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