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Lake County, South Dakota
Shrink-swell clay limits houses without basements on 30% of Lake County's mapped land, a higher share than 81% of US counties. A shallow water table limits basements on 27%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 146 flood losses here since 2016, 59% of them in buildings with basements. 57% of homes were built before 1980, against 50% nationally; the median home dates from 1975.
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 Lake County
| Expansive clay (limits slab homes) | 30.5% |
| High water table (limits basements) | 26.6% |
| Septic fields very limited | 92.0% |
| Clay swell (LEP, by area) | 5.4% |
| High-swell land (LEP 6%+) | 26.1% |
| Mapped soil | 367,436 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Egan | 23% | n/a |
| Viborg | 10% | n/a |
| Wentworth | 8% | n/a |
| Worthing | 7% | n/a |
| Huntimer | 7% | n/a |
| Whitewood | 6% | n/a |
How we count · survey areas SD079 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 5.4% by land area here, and 26% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 30% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 30% of Lake County's mapped land has shrink-swell clay.
On 27% of Lake 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: 18.52 in, 8.10 in below the 1991-2020 average year of 26.62 in.
USDA rates 92% 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 52 of the last 52 weeks; the most was 100% of its area, in 31 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 | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
146 flood losses since 2016, $6.4 million paid. The worst year was 2019, with 146. Foundations of the buildings, where recorded: 59% basements, 25% slabs, 4% crawl spaces, 12% elevated. Median water depth outside the building: 17 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 146 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 26.62 in |
| 12 months to August 2026 | 18.52 in (-8.10) |
| 2025 | 25.14 in (-1.48) |
| Wettest year since 1895 | 2019: 41.74 in |
| Driest year since 1895 | 1976: 12.20 in |
| Days with 1 inch or more, normal at MADISON 2SE (3 mi away) | 5.9 |
Homes
| Housing units | 5,797 |
| Median year built | 1975 |
| Built before 1980 | 57% |
| Built 2000 or later | 21% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $247,600 |
| Single-family detached | 74% |
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 |
|---|---|---|---|
| Moody County, SD | 22 mi | 10% | 36% |
| Miner County, SD | 24 mi | 41% | 28% |
| McCook County, SD | 27 mi | 26% | 33% |
| Brookings County, SD | 29 mi | 10% | 67% |
| Kingsbury County, SD | 30 mi | 30% | 50% |
| Minnehaha County, SD | 30 mi | 17% | 32% |
| Hanson County, SD | 41 mi | 21% | 25% |
| Pipestone County, MN | 43 mi | 8% | 75% |
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