DeKalb County, Illinois · Sycamore
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With 25% of homes built before 1960 and about 50 hard-freeze nights a year, frozen and split pipes are a leading winter risk in the county.
Basements flood here mostly in June. DeKalb County averages 6.9 days a year with an inch of rain or more.
Sewage backups in DeKalb County spike on heavy-rain days, about 6.9 a year, when sewer mains fill up and water finds the lowest drain.
DeKalb County's wettest day in the 2015–2024 record brought 3.11 inches, and about 91 freeze-thaw days a year mean ice dams in some winters.
6% of occupied homes in DeKalb County heat mainly with wood or propane, below the Illinois county median of 16.5%.
With 28 muggy nights a year, mold in DeKalb County can appear within days of a leak. Dry first, then clean.
Local risk profile
About 100,703 people live in DeKalb County, 631 square miles in northern Illinois, in roughly 41,678 homes. Sycamore is the county seat; DeKalb, Sandwich and Genoa are the next largest communities. The county's median home was built in 1978.
37/100 Water Damage Risk Index: Moderate DeKalb County ranks 92 of 102 Illinois counties. See the statewide ranking and method.The three factors where DeKalb County ranks highest compared with other Illinois counties.
DeKalb is on the colder side of Illinois for pipes. It averaged 132 freezing nights a year over 2015–2024, 50 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 7th.
On January 31, 2019 the low fell to about -26°F, and in the stretch ending March 2015 the county went 19 days in a row below freezing. Leaks from split pipes typically appear the day the thaw arrives.
The freeze season here runs November to March, with January the coldest. If you travel then, leave the thermostat at 55°F or above and open sink cabinets on outside walls.
On average the first fall freeze arrives around Oct 22 and the last spring freeze around Apr 24.
DeKalb gets fewer downpours than most Illinois counties, but they still fill basements. About 6.9 days a year bring an inch or more (85th of 102), most often in June, out of 38.5 inches of total precipitation. On October 15, 2017, 3.11 inches fell in a single day. Multi-day storms matter most for basements; the wettest three days on record here totaled 4.94 inches (through July 22, 2017).
The temperature crosses 32°F in both directions on roughly 91 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
53% of homes in DeKalb County predate 1980, below the Illinois county median of 65.9%, which ranks 89th of Illinois's 102 counties.
Since 2000 the county has added enough housing that 26% of homes are that new. Modern PEX and copper rarely fail on their own; the leaks come from connections, appliances and storms.
Renters occupy 39% of homes. If you rent, the building is usually the landlord's to repair, but your belongings are only covered by renters insurance.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 28 times a year here, below the Illinois county median of 51. 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 expectHeating fuel matters for fire risk. In DeKalb County it's 72% utility gas, 22% electric, 6% 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 DeKalb 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 DeKalb. Lee County has the oldest housing nearby, with 72% of homes built before 1980.
By the numbers
| Factor | DeKalb | Illinois median | Rank |
|---|---|---|---|
| Homes built before 1960 | 25% | 38% | 90 of 102 |
| Homes built before 1980 | 53% | 66% | 89 of 102 |
| Homes built 2000 or later | 26% | 15% | 10 of 102 |
| Manufactured or mobile homes | 2.1% | 5.6% | 86 of 102 |
| Vacant homes | 5.1% | 11% | 94 of 102 |
| Wood or propane heat | 5.8% | 17% | 87 of 102 |
| Nights at 20°F or colder | 50/yr | 35/yr | 7 of 102 |
| Days with 1 inch+ of rain | 6.9/yr | 8.4/yr | 85 of 102 |
| Freeze-thaw days | 91/yr | 81/yr | 3 of 102 |
| Muggy nights (65°F+) | 28/yr | 51/yr | 95 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 DeKalb County: freezing from November to March, heavy rain in June, July and October.
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