Boone County, Illinois · Belvidere
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With 26% of homes built before 1960 and about 52 hard-freeze nights a year, frozen and split pipes are a leading winter risk in the county.
July brings the most downpours to Boone County, part of 7.2 heavy-rain days a year. Check the sump first.
26% of homes here predate 1960, when clay and cast iron sewer laterals were standard. Roots and cracks in those lines are a common cause of backups.
In Boone County, 2.82 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
8% of occupied homes in Boone County heat mainly with wood or propane, below the Illinois county median of 16.5%.
With 26 muggy nights a year, mold in Boone County can appear within days of a leak. Dry first, then clean.
Local risk profile
About 53,230 people live in Boone County, 281 square miles in northern Illinois, in roughly 20,291 homes. Besides Belvidere, the county seat, the biggest communities are Candlewick Lake, Poplar Grove and Capron. Much of its housing is recent, with a median build year of 1986.
40/100 Water Damage Risk Index: Moderate Boone County ranks 85 of 102 Illinois counties. See the statewide ranking and method.The three factors where Boone County ranks highest compared with other Illinois counties.
Boone is on the colder side of Illinois for pipes. It averaged 132 freezing nights a year over 2015–2024, 52 of them at 20°F or colder, cold enough for pipes in outside walls and crawl spaces to freeze. Among 102 Illinois counties that's 3rd.
On January 31, 2019 the low fell to about -28°F, and in the stretch ending February 2019 the county went 24 days in a row below freezing. Leaks from split pipes typically appear the day the thaw arrives.
Expect the hardest freezes in January, inside a season that runs November to March. That's when an outdoor spigot left connected to a hose, or a pipe in a crawl space, is most likely to split.
On average the first fall freeze arrives around Oct 22 and the last spring freeze around Apr 27.
Boone gets fewer downpours than most Illinois counties, but they still fill basements. Of roughly 38.6 inches of yearly precipitation, the damage comes from the 7.2 days a year with an inch or more, ranked 76th of 102. June, July and August see the most. The single wettest day in the record: 2.82 inches, September 12, 2022. Multi-day storms matter most for basements; the wettest three days on record here totaled 4.86 inches (through July 16, 2024).
The temperature crosses 32°F in both directions on roughly 89 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
45% of homes in Boone County predate 1980, below the Illinois county median of 65.9%, which ranks 95th of Illinois's 102 counties.
Growth since 2000 added 28% of today's homes. In houses that new, the weak points are washing machine hoses, ice maker lines, water heaters and sump pumps rather than the pipes in the walls.
28% date from 1980 to 1999, the window when polybutylene, a gray flexible plastic supply pipe, was used in some homes. It's prone to leaks at the fittings, so it's worth checking for in a house from those years.
Beyond water
Boone County averages 26 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in July. Mold grows when indoor humidity stays above about 60%, the EPA's ceiling. A basement dehumidifier set to 50% and drying anything wet within 24 to 48 hours prevents most problems.
Mold remediation: what to expectMain heating fuel in Boone County's occupied homes: 78% utility gas, 12% electric, 7% propane and under 1% 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 Boone County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Boone gets more pipe-freeze nights than any of its neighbors. Winnebago County has the oldest housing nearby, with 63% of homes built before 1980.
By the numbers
| Factor | Boone | Illinois median | Rank |
|---|---|---|---|
| Homes built before 1960 | 26% | 38% | 89 of 102 |
| Homes built before 1980 | 45% | 66% | 95 of 102 |
| Homes built 2000 or later | 28% | 15% | 8 of 102 |
| Manufactured or mobile homes | 6% | 5.6% | 48 of 102 |
| Vacant homes | 4.1% | 11% | 97 of 102 |
| Wood or propane heat | 8.3% | 17% | 79 of 102 |
| Nights at 20°F or colder | 52/yr | 35/yr | 3 of 102 |
| Days with 1 inch+ of rain | 7.2/yr | 8.4/yr | 76 of 102 |
| Freeze-thaw days | 89/yr | 81/yr | 11 of 102 |
| Muggy nights (65°F+) | 26/yr | 51/yr | 98 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 Boone County: freezing from November to March, heavy rain in June, July and August.
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