Green County, Wisconsin
Shrink-swell clay limits houses without basements on 30% of Green County's mapped land, a higher share than 80% of US counties and the 8th highest of 72 Wisconsin counties. A shallow water table limits basements on 19%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 13 flood losses here since 2016. 62% of homes were built before 1980, against 50% nationally; the median home dates from 1972.
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 Green County
| Expansive clay (limits slab homes) | 30.2% |
| High water table (limits basements) | 19.0% |
| Septic fields very limited | 85.2% |
| Clay swell (LEP, by area) | 5.3% |
| High-swell land (LEP 6%+) | 39.5% |
| Mapped soil | 374,093 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Newglarus | 18% | n/a |
| Dodgeville | 5% | n/a |
| Sogn | 5% | n/a |
| Edmund | 4% | n/a |
| Palsgrove | 4% | n/a |
| Dunbarton | 3% | n/a |
How we count · survey areas WI045 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 5.3% 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 30% of the mapped land.
On 19% of Green 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: 32.76 in, 5.25 in below the 1991-2020 average year of 38.01 in.
USDA rates 85% 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 35 of the last 52 weeks; the most was 90.7% of its area, in 7 weeks, most recently on the December 23, 2025 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
13 flood losses since 2016, $218,959 paid. The worst year was 2019, with 6.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 2 |
| 2018 | 4 |
| 2019 | 6 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 38.01 in |
| 12 months to August 2026 | 32.76 in (-5.25) |
| 2025 | 30.10 in (-7.91) |
| Wettest year since 1895 | 2018: 51.27 in |
| Driest year since 1895 | 1895: 21.23 in |
| Days with 1 inch or more, normal at MONROE WWTP (6 mi away) | 9.3 |
Homes
| Housing units | 16,480 |
| Median year built | 1972 |
| Built before 1980 | 62% |
| Built 2000 or later | 19% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $250,200 |
| Single-family detached | 77% |
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 |
|---|---|---|---|
| Stephenson County, IL | 23 mi | 13% | 24% |
| Lafayette County, WI | 27 mi | 29% | 14% |
| Rock County, WI | 27 mi | 5% | 31% |
| Dane County, WI | 29 mi | 7% | 34% |
| Winnebago County, IL | 32 mi | 9% | 28% |
| Iowa County, WI | 35 mi | 37% | 12% |
| Jo Daviess County, IL | 38 mi | 17% | 20% |
| Carroll County, IL | 45 mi | 13% | 17% |
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