Monroe County, Illinois
A shallow water table limits basements on 59% of Monroe County's mapped land, a higher share than 73% of US counties. Shrink-swell clay limits houses without basements on 20%.
26.4% of the county is in drought on the October 13, 2026 Drought Monitor map, up from 0% a week earlier. FEMA's flood data list 11 flood losses here since 2016. 41% of homes were built before 1980, against 50% nationally; the median home dates from 1990.
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 Monroe County
| Expansive clay (limits slab homes) | 20.1% |
| High water table (limits basements) | 58.7% |
| Septic fields very limited | 85.2% |
| Clay swell (LEP, by area) | 4.7% |
| High-swell land (LEP 6%+) | 21.8% |
| Mapped soil | 254,355 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Menfro | 18% | 0% |
| Bunkum | 10% | n/a |
| Homen | 7% | n/a |
| Marine | 5% | n/a |
| Fults | 5% | n/a |
| Wakeland | 4% | n/a |
How we count · survey areas IL133 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 4.7% by land area here, and 22% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 20% of the mapped land.
Clay shrinks as it dries: 26.4% of the county is in drought on the latest map, and 20% of Monroe County's mapped land has shrink-swell clay.
On 59% of Monroe 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: 35.43 in, 7.56 in below the 1991-2020 average year of 42.99 in.
USDA rates 85% of the land very limited for septic absorption fields.
Drought
26.4% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 16 of the last 52 weeks; the most was 100% of its area, in 8 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 | 26.4% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
11 flood losses since 2016, $603,788 paid. The worst year was 2019, with 7.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 7 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 0 |
| 2024 | 2 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 42.99 in |
| 12 months to August 2026 | 35.43 in (-7.56) |
| 2025 | 34.55 in (-8.44) |
| Wettest year since 1895 | 1993: 56.01 in |
| Driest year since 1895 | 1953: 23.87 in |
| Days with 1 inch or more, normal at FESTUS (12 mi away) | 12.3 |
Homes
| Housing units | 14,759 |
| Median year built | 1990 |
| Built before 1980 | 41% |
| Built 2000 or later | 32% |
| Owner-occupied | 85% |
| Median value, owner-occupied | $282,100 |
| Single-family detached | 84% |
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. Clair County, IL | 19 mi | 28% | 73% |
| Jefferson County, MO | 20 mi | 37% | 34% |
| Randolph County, IL | 25 mi | 24% | 64% |
| St. Louis city, MO | 25 mi | 1% | 32% |
| Ste. Genevieve County, MO | 27 mi | 16% | 34% |
| St. Louis County, MO | 29 mi | 5% | 37% |
| St. Francois County, MO | 36 mi | 15% | 40% |
| Madison County, IL | 41 mi | 33% | 73% |
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