McLean County, Illinois
A shallow water table limits basements on 85% of McLean County's mapped land, a higher share than 92% of US counties. Shrink-swell clay limits houses without basements on 54%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 27 flood losses here since 2016. 49% 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 McLean County
| Expansive clay (limits slab homes) | 53.8% |
| High water table (limits basements) | 84.5% |
| Septic fields very limited | 89.3% |
| Clay swell (LEP, by area) | 5.0% |
| High-swell land (LEP 6%+) | 19.2% |
| Mapped soil | 759,795 acres |
How we count · survey areas IL113 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 5.0% by land area here, and 19% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 54% of the mapped land.
On 85% of McLean 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: 38.32 in, 0.01 in below the 1991-2020 average year of 38.33 in.
USDA rates 89% 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 26 of the last 52 weeks; the most was 100% of its area, in 24 weeks, most recently on the March 31, 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
27 flood losses since 2016, $369,977 paid. The worst year was 2021, with 14.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 2 |
| 2019 | 2 |
| 2020 | 3 |
| 2021 | 14 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 2 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 38.33 in |
| 12 months to August 2026 | 38.32 in (-0.01) |
| 2025 | 27.24 in (-11.09) |
| Wettest year since 1895 | 1993: 54.62 in |
| Driest year since 1895 | 1988: 23.01 in |
| Days with 1 inch or more, normal at NORMAL 4NE (7 mi away) | 9.3 |
Homes
| Housing units | 75,305 |
| Median year built | 1981 |
| Built before 1980 | 49% |
| Built 2000 or later | 25% |
| Owner-occupied | 65% |
| Median value, owner-occupied | $208,400 |
| Single-family detached | 60% |
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 |
|---|---|---|---|
| De Witt County, IL | 22 mi | 69% | 87% |
| Woodford County, IL | 28 mi | 49% | 81% |
| Livingston County, IL | 32 mi | 53% | 96% |
| Ford County, IL | 33 mi | 55% | 98% |
| Tazewell County, IL | 35 mi | 33% | 53% |
| Piatt County, IL | 36 mi | 57% | 94% |
| Logan County, IL | 37 mi | 45% | 71% |
| Champaign County, IL | 42 mi | 26% | 94% |
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