Waukesha County, Wisconsin
A shallow water table limits basements on 42% of Waukesha County's mapped land, a higher share than 60% of US counties. Shrink-swell clay limits houses without basements on 3%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 122 flood losses here since 2016, 65% of them in buildings with basements. 48% of homes were built before 1980, against 50% nationally; the median home dates from 1981.
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 Waukesha County
| Expansive clay (limits slab homes) | 3.2% |
| High water table (limits basements) | 42.1% |
| Septic fields very limited | 85.6% |
| Clay swell (LEP, by area) | 3.6% |
| High-swell land (LEP 6%+) | 3.0% |
| Mapped soil | 371,530 acres |
How we count · survey areas WI133 (2025-09-10)
What the numbers mean here
On 42% of Waukesha 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: 34.66 in, 0.91 in below the 1991-2020 average year of 35.57 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 5 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
122 flood losses since 2016, $4.8 million paid. The worst year was 2025, with 93. Foundations of the buildings, where recorded: 65% basements, 18% slabs, 8% crawl spaces, 10% elevated. Median water depth outside the building: 14 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 4 |
| 2018 | 6 |
| 2019 | 3 |
| 2020 | 1 |
| 2021 | 0 |
| 2022 | 6 |
| 2023 | 0 |
| 2024 | 2 |
| 2025 | 93 |
| 2026 to date | 7 |
Rain
| Average year, 1991-2020 | 35.57 in |
| 12 months to August 2026 | 34.66 in (-0.91) |
| 2025 | 36.31 in (+0.74) |
| Wettest year since 1895 | 2018: 45.17 in |
| Driest year since 1895 | 1901: 20.22 in |
| Days with 1 inch or more, normal at WAUKESHA WWTP (3 mi away) | 7.9 |
Homes
| Housing units | 175,591 |
| Median year built | 1981 |
| Built before 1980 | 48% |
| Built 2000 or later | 22% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $398,200 |
| Single-family detached | 69% |
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 |
|---|---|---|---|
| Milwaukee County, WI | 23 mi | 8% | 57% |
| Jefferson County, WI | 24 mi | 4% | 57% |
| Washington County, WI | 26 mi | 1% | 44% |
| Walworth County, WI | 27 mi | under 1% | 33% |
| Racine County, WI | 31 mi | 15% | 76% |
| Dodge County, WI | 35 mi | 7% | 59% |
| Kenosha County, WI | 37 mi | 15% | 76% |
| Ozaukee County, WI | 40 mi | 41% | 43% |
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