Putnam County, Illinois · Hennepin
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Putnam County averages 46 nights a year at 20°F or colder, mostly November to March, and 35% of its homes predate 1960.
Heavy rain days of an inch or more come about 5.9 times a year here, most often in June. A sump pump that hasn't run since last season is a common weak point.
Backups often follow heavy rain, which Putnam County gets about 5.9 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 90 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
19% of occupied homes in Putnam 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 36 times a year in Putnam County. Mold after a leak spreads fastest from June through August.
Local risk profile
About 5,601 people live in Putnam County, 160 square miles in northern Illinois, in roughly 3,090 homes. The county seat is Hennepin, and Granville, Mark and Standard round out the largest towns. The county's median home was built in 1975.
38/100 Water Damage Risk Index: Moderate Putnam County ranks 90 of 102 Illinois counties. See the statewide ranking and method.The three factors where Putnam County ranks highest compared with other Illinois counties.
Putnam is on the colder side of Illinois for pipes. In the 2015–2024 record the county logged about 46 nights a year at or below 20°F (17th of 102) and 122 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
On January 31, 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.
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 23 and the last spring freeze around Apr 24.
Putnam gets fewer downpours than most Illinois counties, but they still fill basements. About 5.9 days a year bring an inch or more (102nd of 102), most often in June, out of 37.9 inches of total precipitation. On September 28, 2019, 4.04 inches fell in a single day. Multi-day storms matter most for basements; the wettest three days on record here totaled 4.67 inches (through September 30, 2019).
About 90 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
Illinois's 102 counties range widely in housing age; Putnam ranks 74th, with 58% of its homes built before 1980.
Since 2000 the county has added enough housing that 22% of homes are that new. Modern PEX and copper rarely fail on their own; the leaks come from connections, appliances and storms.
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
About 36 nights a year in Putnam County stay at 65°F or warmer, a sign of muggy summer air (83rd of 102 counties). May is the wettest month. Keep indoor humidity under 60%, as the EPA advises, and dry any leak within 24 to 48 hours; in a humid month a wet basement left alone won't dry by itself.
Mold remediation: what to expectBy main heating fuel, Putnam County homes break down as 67% utility gas, 14% electric, 15% propane and 4% wood. Wood heat is above the Illinois norm. Annual chimney and vent inspection, which the NFPA recommends, is one of the most effective fire-prevention habits for these homes.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Putnam County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Bureau gets more pipe-freeze nights than Putnam. All of its neighbors see more heavy-rain days. Bureau County has the oldest housing nearby, with 79% of homes built before 1980.
By the numbers
| Factor | Putnam | Illinois median | Rank |
|---|---|---|---|
| Homes built before 1960 | 35% | 38% | 66 of 102 |
| Homes built before 1980 | 58% | 66% | 74 of 102 |
| Homes built 2000 or later | 22% | 15% | 16 of 102 |
| Manufactured or mobile homes | 2.5% | 5.6% | 79 of 102 |
| Vacant homes | 20% | 11% | 9 of 102 |
| Wood or propane heat | 19% | 17% | 41 of 102 |
| Nights at 20°F or colder | 46/yr | 35/yr | 17 of 102 |
| Days with 1 inch+ of rain | 5.9/yr | 8.4/yr | 102 of 102 |
| Freeze-thaw days | 90/yr | 81/yr | 7 of 102 |
| Muggy nights (65°F+) | 36/yr | 51/yr | 83 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 Putnam 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