Madison County, Illinois
A shallow water table limits basements on 73% of Madison County's mapped land, a higher share than 84% of US counties. Shrink-swell clay limits houses without basements on 33%.
85.2% of the county is in drought on the October 13, 2026 Drought Monitor map, up from 69.6% a week earlier. FEMA's flood data list 131 flood losses here since 2016, 72% of them in buildings with basements. 61% of homes were built before 1980, against 50% nationally; the median home dates from 1971.
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 Madison County
| Expansive clay (limits slab homes) | 33.4% |
| High water table (limits basements) | 73.2% |
| Septic fields very limited | 85.2% |
| Clay swell (LEP, by area) | 5.1% |
| High-swell land (LEP 6%+) | 31.5% |
| Urban land, not rated | 1.8% |
| Mapped soil | 473,740 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Winfield | 8% | n/a |
| Menfro | 7% | 0% |
| Marine | 7% | n/a |
| Hickory | 6% | n/a |
| Virden | 4% | n/a |
| Wakeland | 4% | n/a |
How we count · survey areas IL119 (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.
Clay shrinks as it dries: 85.2% of the county is in drought on the latest map, and 33% of Madison County's mapped land has shrink-swell clay.
On 73% of Madison 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: 37.59 in, 4.69 in below the 1991-2020 average year of 42.28 in.
USDA rates 85% of the land very limited for septic absorption fields.
Drought
85.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 24 of the last 52 weeks; the most was 100% of its area, in 15 weeks, most recently on the February 10, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 85.2% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
131 flood losses since 2016, $2.3 million paid. The worst year was 2019, with 58. Foundations of the buildings, where recorded: 72% basements, 11% slabs, 11% crawl spaces, 6% elevated. Median water depth outside the building: 5 in.
| Year | Flood losses |
|---|---|
| 2016 | 28 |
| 2017 | 17 |
| 2018 | 1 |
| 2019 | 58 |
| 2020 | 5 |
| 2021 | 2 |
| 2022 | 2 |
| 2023 | 7 |
| 2024 | 7 |
| 2025 | 4 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 42.28 in |
| 12 months to August 2026 | 37.59 in (-4.69) |
| 2025 | 36.97 in (-5.31) |
| Wettest year since 1895 | 2008: 57.01 in |
| Driest year since 1895 | 1953: 25.19 in |
| Days with 1 inch or more, normal at EDWARDSVILLE 2 W (6 mi away) | 12.5 |
Homes
| Housing units | 119,168 |
| Median year built | 1971 |
| Built before 1980 | 61% |
| Built 2000 or later | 19% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $173,000 |
| Single-family detached | 79% |
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 |
|---|---|---|---|
| St. Louis city, MO | 23 mi | 1% | 32% |
| St. Clair County, IL | 25 mi | 28% | 73% |
| Bond County, IL | 25 mi | 47% | 86% |
| Clinton County, IL | 30 mi | 44% | 88% |
| Jersey County, IL | 30 mi | 22% | 53% |
| Macoupin County, IL | 30 mi | 62% | 78% |
| St. Louis County, MO | 32 mi | 5% | 37% |
| Montgomery County, IL | 36 mi | 68% | 88% |
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