Mercer County, Pennsylvania · Mercer
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With 47% of homes built before 1960 and about 41 hard-freeze nights a year, frozen and split pipes are a leading winter risk in the county.
Heavy rain days of an inch or more come about 5.2 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 Mercer County gets about 5.2 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
In Mercer County, 2.68 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
8% of occupied homes in Mercer County heat mainly with wood or propane, below the Pennsylvania county median of 10%.
About 14 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
With 50,930 homes and around 109,257 residents, Mercer County is 673 square miles of western Pennsylvania. Mercer is the county seat; Hermitage, Sharon and Grove City are the next largest communities. Half the homes here were built before 1963, half after.
44/100 Water Damage Risk Index: Moderate Mercer County ranks 46 of 67 Pennsylvania counties. See the statewide ranking and method.The three factors where Mercer County ranks highest compared with other Pennsylvania counties.
Pipe-freeze risk in Mercer County sits near the middle of the state. In the 2015–2024 record the county logged about 41 nights a year at or below 20°F (29th of 67) and 128 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
Cold snaps are the real risk. The worst in the record lasted 17 days below freezing (ending March 2015), and the low bottomed out near -20°F on February 20, 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 24 and end around May 5.
Mercer gets fewer downpours than most Pennsylvania counties, but they still fill basements. Of roughly 45.3 inches of yearly precipitation, the damage comes from the 5.2 days a year with an inch or more, ranked 64th of 67. April, June and September see the most. The single wettest day in the record: 2.68 inches, September 10, 2018. The worst three-day stretch dropped 3.47 inches, ending June 16, 2015, the kind of soaking that overwhelms sump pumps and storm sewers.
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 98 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
73% of homes in Mercer County predate 1980, above the Pennsylvania county median of 66%, which ranks 21st of Pennsylvania's 67 counties.
Before 1960 is when 47% of these homes went up. Galvanized supply lines and cast iron drains were standard then, and after 60-plus years both corrode and crack, often out of sight inside a wall or under a slab.
Manufactured and mobile homes make up 7% of the housing here. Water lines in the underbelly depend on intact skirting and working heat tape, and they're usually the first to freeze in a cold snap.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 14 times a year here, below the Pennsylvania county median of 16. 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, Mercer County homes break down as 63% utility gas, 18% electric, 4% propane and 4% 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 Mercer County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Crawford and Venango get more pipe-freeze nights than Mercer. Lawrence County has the oldest housing nearby, with 77% of homes built before 1980.
By the numbers
| Factor | Mercer | Pennsylvania median | Rank |
|---|---|---|---|
| Homes built before 1960 | 47% | 42% | 23 of 67 |
| Homes built before 1980 | 73% | 66% | 21 of 67 |
| Homes built 2000 or later | 9.7% | 13% | 53 of 67 |
| Manufactured or mobile homes | 7% | 6.6% | 32 of 67 |
| Vacant homes | 8.7% | 12% | 48 of 67 |
| Wood or propane heat | 7.9% | 10% | 43 of 67 |
| Nights at 20°F or colder | 41/yr | 37/yr | 29 of 67 |
| Days with 1 inch+ of rain | 5.2/yr | 7/yr | 64 of 67 |
| Freeze-thaw days | 98/yr | 98/yr | 33 of 67 |
| Muggy nights (65°F+) | 14/yr | 16/yr | 40 of 67 |
Rank 1 is the highest value. Bars run from the lowest to the highest Pennsylvania county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Mercer County: freezing from November to March, heavy rain in April, June 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