Stephenson County, Illinois · Freeport
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Stephenson County averages 56 nights a year at 20°F or colder, mostly November to March, and 51% of its homes predate 1960.
Heavy rain days of an inch or more come about 9 times a year here, most often in July. A sump pump that hasn't run since last season is a common weak point.
Backups often follow heavy rain, which Stephenson County gets about 9 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
Roof leaks here come from summer downpours and, with about 92 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
14% of occupied homes in Stephenson County heat mainly with wood or propane, below the Illinois county median of 16.5%.
Muggy summer nights, lows of 65°F or more, come about 24 times a year in Stephenson County. Mold after a leak spreads fastest from June through August.
Local risk profile
With 21,330 homes and around 43,768 residents, Stephenson County is 564 square miles of northern Illinois. Besides Freeport, the county seat, the biggest communities are Lena, Lake Summerset and Orangeville. The county's median home was built in 1960.
72/100 Water Damage Risk Index: High Stephenson County ranks 1 of 102 Illinois counties. See the statewide ranking and method.The three factors where Stephenson County ranks highest compared with other Illinois counties.
Stephenson is on the colder side of Illinois for pipes. In the 2015–2024 record the county logged about 56 nights a year at or below 20°F (2nd of 102) and 137 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
Cold snaps are the real risk. The worst in the record lasted 17 days below freezing (ending February 2019), and the low bottomed out near -31°F on January 31, 2019.
Most freezing nights fall from November to March, peaking in January. Disconnect garden hoses and shut off outdoor spigots before the first hard frost, and keep the heat at 55°F or higher if you'll be away.
On average the first fall freeze arrives around Oct 18 and the last spring freeze around Apr 29.
Rainfall is about average for Illinois. The county gets about 40.1 inches of rain and melted snow a year, with 9 days of an inch or more (41st of 102). Those downpours cluster in July, August and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.37 inches on July 20, 2017. Multi-day storms matter most for basements; the wettest three days on record here totaled 6.76 inches (through July 22, 2017).
The temperature crosses 32°F in both directions on roughly 92 days a year. Each cycle melts and refreezes water at roof edges and in foundation cracks, which is how ice dams and basement seepage get started.
Housing
Roughly 75% of the county's housing was built before 1980. That puts Stephenson among the oldest housing stocks of Illinois's 102 counties.
Before 1960 is when 51% of these homes went up. Galvanized supply lines and cast iron drains were standard then, and after 60-plus years both corrode and crack, often out of sight inside a wall or under a slab.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 24 times a year here, below the Illinois county median of 51. The EPA recommends keeping indoor humidity below 60%, ideally 30 to 50%. Basements can pass 60% on their own in summer, so a dehumidifier matters even without a leak, and anything wet should be dried within 24 to 48 hours.
Mold remediation: what to expectMain heating fuel in Stephenson County's occupied homes: 67% utility gas, 16% electric, 13% propane and 2% wood. Fires here are likelier to start in the kitchen or the wiring than in the furnace. After any fire, keep the HVAC off until ducts are checked, or soot will travel through the house.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Stephenson County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Jo Daviess gets more pipe-freeze nights than Stephenson. It also has the most heavy-rain days in its area. Its housing is the oldest in the area by share of homes built before 1980.
By the numbers
| Factor | Stephenson | Illinois median | Rank |
|---|---|---|---|
| Homes built before 1960 | 51% | 38% | 11 of 102 |
| Homes built before 1980 | 75% | 66% | 21 of 102 |
| Homes built 2000 or later | 8.6% | 15% | 90 of 102 |
| Manufactured or mobile homes | 3.6% | 5.6% | 69 of 102 |
| Vacant homes | 9.2% | 11% | 69 of 102 |
| Wood or propane heat | 14% | 17% | 63 of 102 |
| Nights at 20°F or colder | 56/yr | 35/yr | 2 of 102 |
| Days with 1 inch+ of rain | 9/yr | 8.4/yr | 41 of 102 |
| Freeze-thaw days | 92/yr | 81/yr | 1 of 102 |
| Muggy nights (65°F+) | 24/yr | 51/yr | 102 of 102 |
Rank 1 is the highest value. Bars run from the lowest to the highest Illinois county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Stephenson County: freezing from November to March, heavy rain in July, August and September.
Sources: U.S. Census Bureau, ACS 2024 5-year estimates (2020-2024); weather from NOAA nClimGrid-Daily county averages (EpiNOAA), 2015–2024, averaged across the county; county boundaries from Census TIGER. Reviewed 2026-10-21. Methodology