Cass County, Illinois
A shallow water table limits basements on 45% of Cass County's mapped land, a higher share than 62% of US counties. Shrink-swell clay limits houses without basements on 13%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 6 flood losses here since 2016. 66% of homes were built before 1980, against 50% nationally; the median home dates from 1968.
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 Cass County
| Expansive clay (limits slab homes) | 13.5% |
| High water table (limits basements) | 44.8% |
| Septic fields very limited | 69.9% |
| Clay swell (LEP, by area) | 3.5% |
| High-swell land (LEP 6%+) | 10.9% |
| Mapped soil | 245,325 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Ipava | 7% | 100% |
| Plainfield | 6% | 2% |
| Sylvan | 6% | n/a |
| Quiver | 5% | n/a |
| Fayette | 4% | 0% |
| Bold | 4% | n/a |
How we count · survey areas IL017 (2025-09-01)
What the numbers mean here
On 45% of Cass 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: 37.06 in, 1.29 in below the 1991-2020 average year of 38.35 in.
USDA rates 70% 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 24 of the last 52 weeks; the most was 100% of its area, in 21 weeks, most recently on the March 10, 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
6 flood losses since 2016, $36,020 paid. The worst year was 2016, with 3.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 1 |
| 2020 | 2 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 38.35 in |
| 12 months to August 2026 | 37.06 in (-1.29) |
| 2025 | 27.23 in (-11.12) |
| Wettest year since 1895 | 1993: 55.57 in |
| Driest year since 1895 | 1901: 23.23 in |
| Days with 1 inch or more, normal at VIRGINIA (2 mi away) | 10 |
Homes
| Housing units | 5,676 |
| Median year built | 1968 |
| Built before 1980 | 66% |
| Built 2000 or later | 13% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $97,100 |
| Single-family detached | 80% |
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 |
|---|---|---|---|
| Morgan County, IL | 18 mi | 43% | 54% |
| Schuyler County, IL | 23 mi | 31% | 46% |
| Menard County, IL | 24 mi | 27% | 51% |
| Mason County, IL | 26 mi | 3% | 42% |
| Scott County, IL | 26 mi | 27% | 47% |
| Brown County, IL | 27 mi | 29% | 38% |
| Sangamon County, IL | 34 mi | 58% | 72% |
| Fulton County, IL | 34 mi | 24% | 38% |
Sources: USDA SSURGO (September 1, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status