Union County, Illinois
A shallow water table limits basements on 49% of Union County's mapped land, a higher share than 65% of US counties. Shrink-swell clay limits houses without basements on 10%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map, up from 50.8% a week earlier. FEMA's flood data list 6 flood losses here since 2016. 59% of homes were built before 1980, against 50% nationally; the median home dates from 1975.
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 Union County
| Expansive clay (limits slab homes) | 9.6% |
| High water table (limits basements) | 48.6% |
| Septic fields very limited | 76.3% |
| Clay swell (LEP, by area) | 4.3% |
| High-swell land (LEP 6%+) | 10.9% |
| Mapped soil | 270,285 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Menfro | 27% | 0% |
| Hosmer | 23% | over 99% |
| Wakeland | 6% | n/a |
| Clarksville | 4% | 0% |
| Haymond | 3% | n/a |
| Karnak | 3% | n/a |
How we count · survey areas IL181 (2025-08-31)
What the numbers mean here
On 49% of Union 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: 38.67 in, 10.06 in below the 1991-2020 average year of 48.73 in.
USDA rates 76% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 27 of the last 52 weeks; the most was 100% of its area, in 5 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
6 flood losses since 2016, $71,854 paid. The worst year was 2016, with 3.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 2 |
| 2020 | 1 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 48.73 in |
| 12 months to August 2026 | 38.67 in (-10.06) |
| 2025 | 45.19 in (-3.54) |
| Wettest year since 1895 | 1945: 70.74 in |
| Driest year since 1895 | 1953: 29.68 in |
| Days with 1 inch or more, normal at CARBONDALE SEWAGE PLT (17 mi away) | 13 |
Homes
| Housing units | 7,851 |
| Median year built | 1975 |
| Built before 1980 | 59% |
| Built 2000 or later | 19% |
| Owner-occupied | 77% |
| Median value, owner-occupied | $131,700 |
| Single-family detached | 75% |
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 |
|---|---|---|---|
| Pulaski County, IL | 20 mi | 10% | 72% |
| Johnson County, IL | 20 mi | 2% | 78% |
| Alexander County, IL | 22 mi | 19% | 48% |
| Jackson County, IL | 22 mi | 26% | 62% |
| Williamson County, IL | 24 mi | 16% | 74% |
| Cape Girardeau County, MO | 25 mi | 3% | 24% |
| Ballard County, KY | 33 mi | 2% | 67% |
| Perry County, MO | 34 mi | 19% | 32% |
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