Jersey County, Illinois
A shallow water table limits basements on 53% of Jersey County's mapped land, a higher share than 69% of US counties. Shrink-swell clay limits houses without basements on 22%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 121 flood losses here since 2016, 24% of them in buildings with basements. 57% 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 Jersey County
| Expansive clay (limits slab homes) | 21.6% |
| High water table (limits basements) | 53.2% |
| Septic fields very limited | 72.7% |
| Clay swell (LEP, by area) | 4.4% |
| High-swell land (LEP 6%+) | 12.6% |
| Mapped soil | 241,790 acres |
How we count · survey areas IL083 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 4.4% by land area here, and 13% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 22% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 22% of Jersey County's mapped land has shrink-swell clay.
On 53% of Jersey 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: 32.95 in, 8.16 in below the 1991-2020 average year of 41.11 in.
USDA rates 73% 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 17 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
121 flood losses since 2016, $5.1 million paid. The worst year was 2019, with 92. Foundations of the buildings, where recorded: 24% basements, 26% slabs, 5% crawl spaces, 45% elevated. Median water depth outside the building: 46 in.
| Year | Flood losses |
|---|---|
| 2016 | 5 |
| 2017 | 18 |
| 2018 | 1 |
| 2019 | 92 |
| 2020 | 1 |
| 2021 | 1 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 3 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 41.11 in |
| 12 months to August 2026 | 32.95 in (-8.16) |
| 2025 | 33.35 in (-7.76) |
| Wettest year since 1895 | 2008: 58.44 in |
| Driest year since 1895 | 1901: 22.84 in |
| Days with 1 inch or more, normal at JERSEYVILLE 2 SW (2 mi away) | 11.1 |
Homes
| Housing units | 9,958 |
| Median year built | 1975 |
| Built before 1980 | 57% |
| Built 2000 or later | 23% |
| Owner-occupied | 81% |
| Median value, owner-occupied | $171,900 |
| Single-family detached | 86% |
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 |
|---|---|---|---|
| Calhoun County, IL | 17 mi | 4% | 25% |
| Greene County, IL | 19 mi | 20% | 51% |
| Macoupin County, IL | 27 mi | 62% | 78% |
| St. Charles County, MO | 27 mi | 41% | 62% |
| Madison County, IL | 30 mi | 33% | 73% |
| St. Louis County, MO | 31 mi | 5% | 37% |
| St. Louis city, MO | 31 mi | 1% | 32% |
| Lincoln County, MO | 32 mi | 64% | 55% |
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