DuPage County, Illinois
A shallow water table limits basements on 90% of DuPage County's mapped land, a higher share than 96% 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 198 flood losses here since 2016, 77% of them in buildings with basements. 54% of homes were built before 1980, against 50% nationally; the median home dates from 1978.
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 DuPage County
| Expansive clay (limits slab homes) | 33.3% |
| High water table (limits basements) | 90.3% |
| Septic fields very limited | 96.1% |
| Clay swell (LEP, by area) | 5.1% |
| High-swell land (LEP 6%+) | 31.1% |
| Urban land, not rated | 1.0% |
| Mapped soil | 215,455 acres |
How we count · survey areas IL043 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 5.1% by land area here, and 31% 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 90% of DuPage 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: 41.69 in, 3.26 in above the 1991-2020 average year of 38.43 in.
USDA rates 96% 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 12 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
198 flood losses since 2016, $3.7 million paid. The worst year was 2020, with 67. Foundations of the buildings, where recorded: 77% basements, 14% slabs, 4% crawl spaces, 5% elevated. Median water depth outside the building: 8 in.
| Year | Flood losses |
|---|---|
| 2016 | 12 |
| 2017 | 42 |
| 2018 | 14 |
| 2019 | 12 |
| 2020 | 67 |
| 2021 | 2 |
| 2022 | 3 |
| 2023 | 2 |
| 2024 | 4 |
| 2025 | 7 |
| 2026 to date | 33 |
Rain
| Average year, 1991-2020 | 38.43 in |
| 12 months to August 2026 | 41.69 in (+3.26) |
| 2025 | 30.66 in (-7.77) |
| Wettest year since 1895 | 2019: 51.15 in |
| Driest year since 1895 | 1956: 22.96 in |
| Days with 1 inch or more, normal at AURORA (12 mi away) | 9.2 |
Homes
| Housing units | 367,152 |
| Median year built | 1978 |
| Built before 1980 | 54% |
| Built 2000 or later | 15% |
| Owner-occupied | 73% |
| Median value, owner-occupied | $391,400 |
| Single-family detached | 58% |
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 |
|---|---|---|---|
| Kane County, IL | 19 mi | 8% | 82% |
| Cook County, IL | 23 mi | 25% | 59% |
| Kendall County, IL | 25 mi | 26% | 85% |
| Lake County, IL | 27 mi | 16% | 87% |
| Will County, IL | 28 mi | 24% | 85% |
| DeKalb County, IL | 35 mi | 28% | 98% |
| McHenry County, IL | 38 mi | 2% | 54% |
| Grundy County, IL | 42 mi | 30% | 85% |
Sources: USDA SSURGO (August 31, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status