HomeSouth DakotaClay County
Clay County, South Dakota
A shallow water table limits basements on 53% of Clay County's mapped land, a higher share than 69% of US counties. Shrink-swell clay limits houses without basements on 29%.
52.6% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 1 flood losses here since 2016. 56% of homes were built before 1980, against 50% nationally; the median home dates from 1976.
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 Clay County
| Expansive clay (limits slab homes) | 28.8% |
| High water table (limits basements) | 53.1% |
| Septic fields very limited | 87.7% |
| Clay swell (LEP, by area) | 5.7% |
| High-swell land (LEP 6%+) | 31.4% |
| Mapped soil | 267,654 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Egan | 19% | n/a |
| Luton | 6% | n/a |
| Trent | 6% | n/a |
| Clarno | 6% | 0% |
| Chancellor | 6% | n/a |
| Ethan | 6% | n/a |
How we count · survey areas SD027 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 5.7% by land area here, and 31% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 29% of the mapped land.
Clay shrinks as it dries: 52.6% of the county is in drought on the latest map, and 29% of Clay County's mapped land has shrink-swell clay.
On 53% of Clay County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 16.67 in, 11.31 in below the 1991-2020 average year of 27.98 in.
USDA rates 88% of the land very limited for septic absorption fields.
Drought
52.6% 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 43 weeks, most recently on the September 8, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 52.6% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
1 flood losses since 2016, $2,000 paid. The worst year was 2024, with 1.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 27.98 in |
| 12 months to August 2026 | 16.67 in (-11.31) |
| 2025 | 26.29 in (-1.69) |
| Wettest year since 1895 | 1944: 39.31 in |
| Driest year since 1895 | 1976: 14.03 in |
| Days with 1 inch or more, normal at CENTERVILLE 6 SE (10 mi away) | 5.6 |
Homes
| Housing units | 6,262 |
| Median year built | 1976 |
| Built before 1980 | 56% |
| Built 2000 or later | 28% |
| Owner-occupied | 51% |
| Median value, owner-occupied | $232,300 |
| Single-family detached | 53% |
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 |
|---|---|---|---|
| Union County, SD | 18 mi | 33% | 42% |
| Yankton County, SD | 22 mi | 21% | 30% |
| Cedar County, NE | 26 mi | 2% | 7% |
| Lincoln County, SD | 28 mi | 28% | 51% |
| Turner County, SD | 28 mi | 20% | 39% |
| Dixon County, NE | 30 mi | 2% | 9% |
| Plymouth County, IA | 41 mi | 8% | 27% |
| Dakota County, NE | 42 mi | 13% | 22% |
Sources: USDA SSURGO (September 10, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status