Jefferson County, Wisconsin
A shallow water table limits basements on 57% of Jefferson County's mapped land, a higher share than 72% of US counties. Shrink-swell clay limits houses without basements on 4%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 15 flood losses here since 2016. 59% of homes were built before 1980, against 50% nationally; the median home dates from 1973.
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 Jefferson County
| Expansive clay (limits slab homes) | 4.3% |
| High water table (limits basements) | 56.6% |
| Septic fields very limited | 86.4% |
| Clay swell (LEP, by area) | 3.4% |
| High-swell land (LEP 6%+) | 5.1% |
| Mapped soil | 373,043 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Kidder | 12% | n/a |
| Houghton | 8% | n/a |
| Fox | 5% | 1% |
| Wacousta | 5% | n/a |
| Sebewa | 5% | n/a |
| Palms | 4% | n/a |
How we count · survey areas WI055 (2025-09-10)
What the numbers mean here
On 57% of Jefferson 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: 33.39 in, 2.69 in below the 1991-2020 average year of 36.08 in.
USDA rates 86% 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 9 of the last 52 weeks; the most was 100% of its area, in 2 weeks, most recently on the June 9, 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
15 flood losses since 2016, $563,637 paid. The worst year was 2026, with 4.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 0 |
| 2018 | 3 |
| 2019 | 4 |
| 2020 | 0 |
| 2021 | 1 |
| 2022 | 1 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 36.08 in |
| 12 months to August 2026 | 33.39 in (-2.69) |
| 2025 | 31.84 in (-4.24) |
| Wettest year since 1895 | 2018: 49.75 in |
| Driest year since 1895 | 1901: 20.63 in |
| Days with 1 inch or more, normal at LAKE MILLS WWTP (8 mi away) | 8.9 |
Homes
| Housing units | 36,890 |
| Median year built | 1973 |
| Built before 1980 | 59% |
| Built 2000 or later | 20% |
| Owner-occupied | 73% |
| Median value, owner-occupied | $274,100 |
| Single-family detached | 72% |
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 |
|---|---|---|---|
| Waukesha County, WI | 24 mi | 3% | 42% |
| Walworth County, WI | 27 mi | under 1% | 33% |
| Rock County, WI | 28 mi | 5% | 31% |
| Dodge County, WI | 29 mi | 7% | 59% |
| Dane County, WI | 33 mi | 7% | 34% |
| Washington County, WI | 38 mi | 1% | 44% |
| Columbia County, WI | 42 mi | 1% | 48% |
| Milwaukee County, WI | 47 mi | 8% | 57% |
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