Blair County, Pennsylvania · Hollidaysburg
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Pipes freeze in Blair County on about 37 nights a year, mostly November to March. Older homes, 54% of the stock here, are most at risk.
Heavy rain days of an inch or more come about 5.9 times a year here, most often in September. A sump pump that hasn't run since last season is a common weak point.
Sewage backups in Blair County spike on heavy-rain days, about 5.9 a year, when sewer mains fill up and water finds the lowest drain.
Roof leaks here come from summer downpours and, with about 100 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
5% of occupied homes in Blair County heat mainly with wood or propane, below the Pennsylvania county median of 10%.
About 16 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
About 121,277 people live in Blair County, 525 square miles in southern Pennsylvania, in roughly 55,901 homes. The county seat is Hollidaysburg, and Altoona, Tyrone and Greenwood round out the largest towns. It has some of the oldest housing in the state: the median home went up in 1957.
53/100 Water Damage Risk Index: Elevated Blair County ranks 26 of 67 Pennsylvania counties. See the statewide ranking and method.The three factors where Blair County ranks highest compared with other Pennsylvania counties.
Pipe-freeze risk in Blair County sits near the middle of the state. From 2015–2024 it averaged 37 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 125 nights at or below 32°F. That ranks 34th of 67 counties.
Cold snaps are the real risk. The worst in the record lasted 14 days below freezing (ending January 2018), and the low bottomed out near -11°F on February 24, 2015.
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 20 and end around Apr 29.
Blair gets fewer downpours than most Pennsylvania counties, but they still fill basements. Of roughly 43.9 inches of yearly precipitation, the damage comes from the 5.9 days a year with an inch or more, ranked 50th of 67. May, June and September see the most. The single wettest day in the record: 3.02 inches, September 10, 2018. The worst three-day stretch dropped 5.54 inches, ending September 11, 2018, the kind of soaking that overwhelms sump pumps and storm sewers.
The temperature crosses 32°F in both directions on roughly 100 days a year. Each cycle melts and refreezes water at roof edges and in foundation cracks, which is how ice dams and basement seepage get started.
Housing
Roughly 75% of the county's housing was built before 1980. That puts Blair among the oldest housing stocks of Pennsylvania's 67 counties.
Before 1960 is when 54% 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.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 16 times a year here, close to the Pennsylvania county median of 16. 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, Blair County homes break down as 57% utility gas, 17% electric, 2% propane and 3% wood. Heating equipment, cooking and electrical failures cause most home fires nationally. Even a small kitchen fire can leave soot through the whole house, because smoke follows air currents into closets, ducts and attic space.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Blair County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Cambria, Centre and Clearfield get more pipe-freeze nights than Blair. Cambria County has the oldest housing nearby, with 80% of homes built before 1980.
By the numbers
| Factor | Blair | Pennsylvania median | Rank |
|---|---|---|---|
| Homes built before 1960 | 54% | 42% | 11 of 67 |
| Homes built before 1980 | 75% | 66% | 13 of 67 |
| Homes built 2000 or later | 9.7% | 13% | 53 of 67 |
| Manufactured or mobile homes | 6.3% | 6.6% | 37 of 67 |
| Vacant homes | 9.6% | 12% | 42 of 67 |
| Wood or propane heat | 4.7% | 10% | 61 of 67 |
| Nights at 20°F or colder | 37/yr | 37/yr | 34 of 67 |
| Days with 1 inch+ of rain | 5.9/yr | 7/yr | 50 of 67 |
| Freeze-thaw days | 100/yr | 98/yr | 25 of 67 |
| Muggy nights (65°F+) | 16/yr | 16/yr | 34 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 Blair County: freezing from November to March, heavy rain in May, 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