Winnebago County, Wisconsin
A shallow water table limits basements on 48% of Winnebago County's mapped land, a higher share than 65% of US counties. Shrink-swell clay limits houses without basements on 33%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 42 flood losses here since 2016, 25% 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 Winnebago County
| Expansive clay (limits slab homes) | 33.4% |
| High water table (limits basements) | 47.9% |
| Septic fields very limited | 69.6% |
| Clay swell (LEP, by area) | 5.4% |
| High-swell land (LEP 6%+) | 39.6% |
| Mapped soil | 370,598 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Kewaunee | 11% | n/a |
| Manawa | 9% | n/a |
| Hortonville | 6% | n/a |
| Houghton | 3% | n/a |
| Zittau | 3% | n/a |
| Menasha | 3% | n/a |
How we count · survey areas WI139 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 5.4% by land area here, and 40% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 33% of the mapped land.
On 48% of Winnebago 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: 30.70 in, 2.08 in below the 1991-2020 average year of 32.78 in.
USDA rates 70% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 16 of the last 52 weeks; the most was 100% of its area, in 4 weeks, most recently on the September 1, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
42 flood losses since 2016, $846,901 paid. The worst year was 2026, with 26. Foundations of the buildings, where recorded: 25% basements, 31% slabs, 36% crawl spaces, 8% elevated. Median water depth outside the building: 8.5 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 2 |
| 2019 | 7 |
| 2020 | 1 |
| 2021 | 2 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 2 |
| 2025 | 2 |
| 2026 to date | 26 |
Rain
| Average year, 1991-2020 | 32.78 in |
| 12 months to August 2026 | 30.70 in (-2.08) |
| 2025 | 29.41 in (-3.37) |
| Wettest year since 1895 | 2019: 44.16 in |
| Driest year since 1895 | 1895: 18.24 in |
| Days with 1 inch or more, normal at OSHKOSH (7 mi away) | 6.2 |
Homes
| Housing units | 77,318 |
| Median year built | 1975 |
| Built before 1980 | 57% |
| Built 2000 or later | 20% |
| Owner-occupied | 66% |
| Median value, owner-occupied | $225,800 |
| 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 |
|---|---|---|---|
| Calumet County, WI | 23 mi | 44% | 42% |
| Fond du Lac County, WI | 24 mi | 13% | 50% |
| Outagamie County, WI | 25 mi | 20% | 54% |
| Green Lake County, WI | 26 mi | 2% | 48% |
| Waushara County, WI | 28 mi | 5% | 36% |
| Waupaca County, WI | 31 mi | 1% | 46% |
| Marquette County, WI | 41 mi | 1% | 41% |
| Brown County, WI | 43 mi | 47% | 32% |
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