Stephenson County, Illinois
A shallow water table limits basements on 24% of Stephenson County's mapped land. 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 89 flood losses here since 2016, 70% of them in buildings with basements. 75% of homes were built before 1980, against 50% nationally; the median home dates from 1960.
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 Stephenson County
| Expansive clay (limits slab homes) | 12.9% |
| High water table (limits basements) | 24.0% |
| Septic fields very limited | 58.5% |
| Clay swell (LEP, by area) | 4.7% |
| High-swell land (LEP 6%+) | 15.1% |
| Mapped soil | 361,390 acres |
How we count · survey areas IL177 (2025-08-31)
What the numbers mean here
On 24% of Stephenson 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: 31.60 in, 6.86 in below the 1991-2020 average year of 38.46 in.
USDA rates 59% 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 28 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
89 flood losses since 2016, $2.8 million paid. The worst year was 2017, with 35. Foundations of the buildings, where recorded: 70% basements, 26% slabs, 4% elevated. Median water depth outside the building: 23 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 35 |
| 2018 | 11 |
| 2019 | 26 |
| 2020 | 1 |
| 2021 | 0 |
| 2022 | 14 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 38.46 in |
| 12 months to August 2026 | 31.60 in (-6.86) |
| 2025 | 29.62 in (-8.84) |
| Wettest year since 1895 | 2019: 51.19 in |
| Driest year since 1895 | 1910: 20.07 in |
| Days with 1 inch or more, normal at FREEPORT WASTE WTP (5 mi away) | 9.2 |
Homes
| Housing units | 21,330 |
| Median year built | 1960 |
| Built before 1980 | 75% |
| Built 2000 or later | 9% |
| Owner-occupied | 71% |
| Median value, owner-occupied | $134,900 |
| Single-family detached | 76% |
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 |
|---|---|---|---|
| Green County, WI | 23 mi | 30% | 19% |
| Carroll County, IL | 23 mi | 13% | 17% |
| Winnebago County, IL | 26 mi | 9% | 28% |
| Ogle County, IL | 28 mi | 10% | 35% |
| Jo Daviess County, IL | 28 mi | 17% | 20% |
| Lafayette County, WI | 32 mi | 29% | 14% |
| Rock County, WI | 37 mi | 5% | 31% |
| Boone County, IL | 43 mi | 6% | 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