Henderson County, Illinois · Oquawka
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Henderson County averages 44 nights a year at 20°F or colder, mostly November to March, and 37% of its homes predate 1960.
Heavy rain days of an inch or more come about 7.5 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 Henderson County gets about 7.5 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
In Henderson County, 2.85 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
25% of occupied homes in Henderson County heat mainly with wood or propane, above the Illinois county median of 16.5%.
Muggy summer nights, lows of 65°F or more, come about 46 times a year in Henderson County. Mold after a leak spreads fastest from June through August.
Local risk profile
Henderson County covers 379 square miles of northwest Illinois, with about 6,193 residents and 3,366 homes. Oquawka is the county seat; Stronghurst, Dallas City and Lomax are the next largest communities. Half the homes here were built before 1972, half after.
49/100 Water Damage Risk Index: Elevated Henderson County ranks 57 of 102 Illinois counties. See the statewide ranking and method.The three factors where Henderson County ranks highest compared with other Illinois counties.
Henderson County gets more hard-freeze nights than most of Illinois. From 2015–2024 it averaged 44 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 119 nights at or below 32°F. That ranks 23rd of 102 counties.
On January 31, 2019 the low fell to about -22°F, and in the stretch ending January 2018 the county went 15 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 23 and end around Apr 21.
Henderson gets fewer downpours than most Illinois counties, but they still fill basements. The county gets about 35.9 inches of rain and melted snow a year, with 7.5 days of an inch or more (70th of 102). Those downpours cluster in June, July and August, when sump pumps and gutters are tested hardest. The wettest day on record brought 2.85 inches on September 28, 2019. The worst three-day stretch dropped 4.11 inches, ending August 7, 2023, the kind of soaking that overwhelms sump pumps and storm sewers.
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 86 times a year here. They're the main driver of ice dams and of water working its way through foundation cracks in late winter.
Housing
Illinois's 102 counties range widely in housing age; Henderson ranks 48th, with 67% of its homes built before 1980.
Housing age is mixed: 37% of homes are pre-1960 and 11% are 2000 or newer. Ask any plumber which era your house is from and you'll know which failures to watch for.
About 22% of homes went up between 1980 and 1999. Some houses from the late 1970s to the mid-1990s were plumbed with polybutylene, a gray plastic pipe known for failing at fittings. A plumber can tell you in a few minutes whether you have it.
Here 13% of housing is manufactured homes. Check the skirting and the heat tape on the main water line every fall, because that one exposed line is what freezes.
20% of homes were vacant at survey time. A leak in an empty rental or seasonal house can run for days before anyone notices, which is why those losses tend to be larger.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 46 times a year here, close to 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 expectBy main heating fuel, Henderson County homes break down as 63% utility gas, 11% electric, 24% propane and under 1% wood. Propane heat is more common here than the state median. Have chimneys swept and fuel-burning appliances serviced each fall, and keep three feet clear around stoves and space heaters.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Henderson County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Mercer and Warren get more pipe-freeze nights than Henderson. Warren County has the oldest housing nearby, with 84% of homes built before 1980.
By the numbers
| Factor | Henderson | Illinois median | Rank |
|---|---|---|---|
| Homes built before 1960 | 37% | 38% | 61 of 102 |
| Homes built before 1980 | 67% | 66% | 48 of 102 |
| Homes built 2000 or later | 11% | 15% | 75 of 102 |
| Manufactured or mobile homes | 13% | 5.6% | 18 of 102 |
| Vacant homes | 20% | 11% | 13 of 102 |
| Wood or propane heat | 25% | 17% | 19 of 102 |
| Nights at 20°F or colder | 44/yr | 35/yr | 23 of 102 |
| Days with 1 inch+ of rain | 7.5/yr | 8.4/yr | 70 of 102 |
| Freeze-thaw days | 86/yr | 81/yr | 27 of 102 |
| Muggy nights (65°F+) | 46/yr | 51/yr | 65 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 Henderson 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