Clark County, Illinois
A shallow water table limits basements on 77% of Clark County's mapped land, a higher share than 87% of US counties. Shrink-swell clay limits houses without basements on 29%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 4 flood losses here since 2016. 64% 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 Clark County
| Expansive clay (limits slab homes) | 28.6% |
| High water table (limits basements) | 77.4% |
| Septic fields very limited | 95.0% |
| Clay swell (LEP, by area) | 4.9% |
| High-swell land (LEP 6%+) | 39.9% |
| Mapped soil | 323,685 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Stoy | 10% | n/a |
| Hickory | 10% | n/a |
| Cisne | 8% | n/a |
| Whitson | 8% | n/a |
| Shoals | 7% | n/a |
| Bluford | 5% | 100% |
How we count · survey areas IL023 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 4.9% by land area here, and 40% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 29% of the mapped land.
On 77% of Clark 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: 41.86 in, 2.04 in below the 1991-2020 average year of 43.90 in.
USDA rates 95% 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 22 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the March 3, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 46.9% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
4 flood losses since 2016, $18,581 paid. The worst year was 2016, with 2.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 1 |
| 2018 | 1 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 43.90 in |
| 12 months to August 2026 | 41.86 in (-2.04) |
| 2025 | 36.44 in (-7.46) |
| Wettest year since 1895 | 2008: 55.90 in |
| Driest year since 1895 | 1914: 27.99 in |
| Days with 1 inch or more, normal at CASEY (10 mi away) | 12.1 |
Homes
| Housing units | 7,307 |
| Median year built | 1971 |
| Built before 1980 | 64% |
| Built 2000 or later | 17% |
| Owner-occupied | 80% |
| Median value, owner-occupied | $132,400 |
| Single-family detached | 82% |
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 |
|---|---|---|---|
| Vigo County, IN | 22 mi | 1% | 58% |
| Crawford County, IL | 23 mi | 43% | 81% |
| Edgar County, IL | 24 mi | 16% | 83% |
| Cumberland County, IL | 24 mi | 39% | 84% |
| Coles County, IL | 26 mi | 19% | 85% |
| Sullivan County, IN | 26 mi | 2% | 61% |
| Jasper County, IL | 30 mi | 51% | 89% |
| Clay County, IN | 36 mi | 2% | 69% |
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