Franklin County, Illinois
A shallow water table limits basements on 88% of Franklin County's mapped land, a higher share than 95% of US counties. Shrink-swell clay limits houses without basements on 31%.
100% 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 7 flood losses here since 2016. 70% of homes were built before 1980, against 50% nationally; the median home dates from 1963.
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 Franklin County
| Expansive clay (limits slab homes) | 31.4% |
| High water table (limits basements) | 88.1% |
| Septic fields very limited | 89.3% |
| Clay swell (LEP, by area) | 4.8% |
| High-swell land (LEP 6%+) | 41.4% |
| Mapped soil | 276,300 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Bluford | 18% | 100% |
| Ava | 13% | n/a |
| Belknap | 10% | n/a |
| Bonnie | 7% | n/a |
| Hoyleton | 7% | n/a |
| Wynoose | 6% | n/a |
How we count · survey areas IL055 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 4.8% by land area here, and 41% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 31% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 31% of Franklin County's mapped land has shrink-swell clay.
On 88% of Franklin 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: 29.52 in, 17.45 in below the 1991-2020 average year of 46.97 in.
USDA rates 89% 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 29 of the last 52 weeks; the most was 100% of its area, in 12 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
7 flood losses since 2016, $112,374 paid. The worst year was 2017, with 5.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 5 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 1 |
| 2021 | 1 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 46.97 in |
| 12 months to August 2026 | 29.52 in (-17.45) |
| 2025 | 35.98 in (-10.99) |
| Wettest year since 1895 | 2011: 68.34 in |
| Driest year since 1895 | 1953: 25.92 in |
| Days with 1 inch or more, normal at W FRANKFORT (6 mi away) | 12.8 |
Homes
| Housing units | 18,462 |
| Median year built | 1963 |
| Built before 1980 | 70% |
| Built 2000 or later | 14% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $89,000 |
| Single-family detached | 79% |
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 |
|---|---|---|---|
| Williamson County, IL | 18 mi | 16% | 74% |
| Jefferson County, IL | 21 mi | 26% | 87% |
| Hamilton County, IL | 22 mi | 23% | 95% |
| Perry County, IL | 25 mi | 24% | 75% |
| Saline County, IL | 27 mi | 20% | 86% |
| Jackson County, IL | 29 mi | 26% | 62% |
| Washington County, IL | 37 mi | 36% | 91% |
| Johnson County, IL | 37 mi | 2% | 78% |
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