LaSalle County, Illinois · Ottawa
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With 47% of homes built before 1960 and about 46 hard-freeze nights a year, frozen and split pipes are a leading winter risk in the county.
June brings the most downpours to LaSalle County, part of 6.3 heavy-rain days a year. Check the sump first.
47% 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.
LaSalle County's wettest day in the 2015–2024 record brought 3.64 inches, and about 88 freeze-thaw days a year mean ice dams in some winters.
9% of occupied homes in LaSalle 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 34 times a year in LaSalle County. Mold after a leak spreads fastest from June through August.
Local risk profile
With 49,843 homes and around 108,714 residents, LaSalle County is 1,135 square miles of northern Illinois. Besides Ottawa, the county seat, the biggest communities are Streator, Peru and LaSalle. Half the homes here were built before 1963, half after.
51/100 Water Damage Risk Index: Elevated LaSalle County ranks 47 of 102 Illinois counties. See the statewide ranking and method.The three factors where LaSalle County ranks highest compared with other Illinois counties.
LaSalle County gets more hard-freeze nights than most of Illinois. In the 2015–2024 record the county logged about 46 nights a year at or below 20°F (17th of 102) and 123 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
On January 30, 2019 the low fell to about -23°F, and in the stretch ending February 2021 the county went 16 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.
Freezing nights typically start around Oct 25 and end around Apr 24.
LaSalle gets fewer downpours than most Illinois counties, but they still fill basements. The county gets about 38 inches of rain and melted snow a year, with 6.3 days of an inch or more (95th of 102). Those downpours cluster in June, July and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.64 inches on September 28, 2019. The worst three-day stretch dropped 4.23 inches, ending September 30, 2019, the kind of soaking that overwhelms sump pumps and storm sewers.
About 88 days a year swing from below freezing at night to above freezing by day. Those freeze-thaw cycles feed ice dams on roofs, open cracks in foundations and driveways, and stress pipes that are already marginal.
Housing
70% of homes in LaSalle County predate 1980, close to the Illinois county median of 65.9%, which ranks 40th of Illinois's 102 counties.
In LaSalle County 47% of homes are older than 1960. If yours is one of them and the plumbing has never been replaced, expect galvanized steel supply pipe and cast iron drain lines, the two materials most likely to fail quietly.
Beyond water
About 34 nights a year in LaSalle County stay at 65°F or warmer, a sign of muggy summer air (89th of 102 counties). May is the wettest month. 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 LaSalle County's occupied homes: 76% utility gas, 14% electric, 9% 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 LaSalle County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Bureau, DeKalb and Lee get more pipe-freeze nights than LaSalle. Bureau County has the oldest housing nearby, with 79% of homes built before 1980.
By the numbers
| Factor | LaSalle | Illinois median | Rank |
|---|---|---|---|
| Homes built before 1960 | 47% | 38% | 25 of 102 |
| Homes built before 1980 | 70% | 66% | 40 of 102 |
| Homes built 2000 or later | 13% | 15% | 60 of 102 |
| Manufactured or mobile homes | 4.2% | 5.6% | 60 of 102 |
| Vacant homes | 9% | 11% | 71 of 102 |
| Wood or propane heat | 9.4% | 17% | 76 of 102 |
| Nights at 20°F or colder | 46/yr | 35/yr | 17 of 102 |
| Days with 1 inch+ of rain | 6.3/yr | 8.4/yr | 95 of 102 |
| Freeze-thaw days | 88/yr | 81/yr | 19 of 102 |
| Muggy nights (65°F+) | 34/yr | 51/yr | 89 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 LaSalle County: freezing from November to March, heavy rain in June, July 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