Winnebago County, Iowa
A shallow water table limits basements on 82% of Winnebago County's mapped land, a higher share than 90% of US counties. Shrink-swell clay limits houses without basements on 18%.
None 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. 84% of homes were built before 1980, against 50% nationally; the median home dates from 1962.
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) | 18.2% |
| High water table (limits basements) | 81.6% |
| Septic fields very limited | 88.3% |
| Clay swell (LEP, by area) | 4.2% |
| High-swell land (LEP 6%+) | 17.2% |
| Mapped soil | 257,100 acres |
How we count · survey areas IA189 (2025-09-09)
What the numbers mean here
Clay swell averages a linear extensibility of 4.2% by land area here, and 17% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 18% of the mapped land.
On 82% 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: 26.16 in, 8.37 in below the 1991-2020 average year of 34.53 in.
USDA rates 88% 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 20 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the July 28, 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
FEMA's flood data list no flood losses in Winnebago County since 2016.
Rain
| Average year, 1991-2020 | 34.53 in |
| 12 months to August 2026 | 26.16 in (-8.37) |
| 2025 | 38.96 in (+4.43) |
| Wettest year since 1895 | 2018: 46.81 in |
| Driest year since 1895 | 1910: 16.37 in |
| Days with 1 inch or more, normal at LAKE MILLS (11 mi away) | 8.9 |
Homes
| Housing units | 5,077 |
| Median year built | 1962 |
| Built before 1980 | 84% |
| Built 2000 or later | 7% |
| Owner-occupied | 71% |
| Median value, owner-occupied | $135,000 |
| Single-family detached | 81% |
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 |
|---|---|---|---|
| Hancock County, IA | 21 mi | 16% | 87% |
| Faribault County, MN | 23 mi | 37% | 88% |
| Worth County, IA | 25 mi | 10% | 80% |
| Kossuth County, IA | 26 mi | 18% | 90% |
| Freeborn County, MN | 28 mi | 13% | 82% |
| Cerro Gordo County, IA | 32 mi | 6% | 75% |
| Wright County, IA | 45 mi | 27% | 89% |
| Waseca County, MN | 45 mi | 17% | 88% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status