Knox County, Ohio · Mount Vernon
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Knox County averages 36 nights a year at 20°F or colder, mostly November to March, and 38% of its homes predate 1960.
Basements flood here mostly in September. Knox County averages 6.1 days a year with an inch of rain or more.
Sewage backups in Knox County spike on heavy-rain days, about 6.1 a year, when sewer mains fill up and water finds the lowest drain.
Roof leaks here come from summer downpours and, with about 91 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
22% of occupied homes in Knox County heat mainly with wood or propane, above the Ohio county median of 15.9%.
About 21 nights a year here stay at 65°F or warmer, so basements and crawl spaces can grow mold even without a leak.
Local risk profile
Knox County covers 525 square miles of central Ohio, with about 63,142 residents and 26,078 homes. The county seat is Mount Vernon, and Apple Valley, Fredericktown and Gambier round out the largest towns. Half the homes here were built before 1973, half after.
61/100 Water Damage Risk Index: Elevated Knox County ranks 19 of 88 Ohio counties. See the statewide ranking and method.The three factors where Knox County ranks highest compared with other Ohio counties.
Knox County gets more hard-freeze nights than most of Ohio. In the 2015–2024 record the county logged about 36 nights a year at or below 20°F (7th of 88) and 119 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
Cold snaps are the real risk. The worst in the record lasted 19 days below freezing (ending March 2015), and the low bottomed out near -13°F on February 24, 2015.
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.
Freezing nights typically start around Oct 22 and end around Apr 28.
Rainfall is about average for Ohio. Of roughly 43.6 inches of yearly precipitation, the damage comes from the 6.1 days a year with an inch or more, ranked 32nd of 88. March, September and November see the most. The single wettest day in the record: 2.51 inches, August 24, 2023. The worst three-day stretch dropped 4.2 inches, ending September 10, 2018, the kind of soaking that overwhelms sump pumps and storm sewers.
About 91 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
Ohio's 88 counties range widely in housing age; Knox ranks 52nd, with 58% of its homes built before 1980.
Housing age is mixed: 38% of homes are pre-1960 and 20% are 2000 or newer. Ask any plumber which era your house is from and you'll know which failures to watch for.
The 1980s and 1990s account for 22% of the county's homes. If yours is from those decades, look under the sinks and at the water heater for gray plastic pipe stamped PB, which is polybutylene and leak-prone.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 21 times a year here, below the Ohio county median of 35. 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 expectHeating fuel matters for fire risk. In Knox County it's 55% utility gas, 19% electric, 15% propane and 8% wood. Wood heat is more common here than in most Ohio counties. Heating equipment is one of the leading causes of home fires nationally, and the NFPA recommends having chimneys and vents inspected every year.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Knox County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Ashland, Morrow and Richland get more pipe-freeze nights than Knox. It also has the most heavy-rain days in its area. Richland County has the oldest housing nearby, with 74% of homes built before 1980.
By the numbers
| Factor | Knox | Ohio median | Rank |
|---|---|---|---|
| Homes built before 1960 | 38% | 37% | 39 of 88 |
| Homes built before 1980 | 58% | 61% | 52 of 88 |
| Homes built 2000 or later | 20% | 17% | 26 of 88 |
| Manufactured or mobile homes | 4% | 5.9% | 59 of 88 |
| Vacant homes | 9.9% | 8.4% | 30 of 88 |
| Wood or propane heat | 22% | 16% | 23 of 88 |
| Nights at 20°F or colder | 36/yr | 31/yr | 7 of 88 |
| Days with 1 inch+ of rain | 6.1/yr | 5.7/yr | 32 of 88 |
| Freeze-thaw days | 91/yr | 82/yr | 3 of 88 |
| Muggy nights (65°F+) | 21/yr | 35/yr | 85 of 88 |
Rank 1 is the highest value. Bars run from the lowest to the highest Ohio county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Knox County: freezing from November to March, heavy rain in March, September and November.
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