Ice dam risk in Jefferson Hills, PA
Ice dams in Jefferson Hills, PA: how often
6.0 dam days a winter
Moderate risk. On an ordinary house in Jefferson Hills, conditions for an ice dam come on about 6.0 days in a normal winter, mostly in January and February.
Jefferson Hills averages 21 inches of snow a year and about 24 days with snow on the ground. Most of it comes and goes within a few days. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
What your attic does to that number in Jefferson Hills
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.9 | Low |
| Typical, some insulation, not air-sealed | 6.0 | Moderate |
| Older or poorly insulated, warm attic | 8.6 | Moderate |
Sealing and insulating a typical attic takes out about 2.1 days a winter here. It drops the risk from moderate to low.
Preventing ice dams on a Jefferson Hills roof
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
- Rake the bottom three or four feet of roof after any storm that leaves more than about six inches, from the ground with a roof rake.
Which to spend on first: air sealing or heat cable.
Jefferson Hills winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.7 | 8.8 | 2.5 |
| February | 7.2 | 7.1 | 1.8 |
| March | 4.6 | 2.6 | 0.4 |
| April | 0.1 | 0.1 | 0.0 |
| November | 0.5 | 0.5 | 0.1 |
| December | 3.3 | 5.0 | 1.2 |
Jefferson Hills next to nearby towns
Jefferson Hills ranks 58 of 68 Pennsylvania cities here for ice-dam days, behind St. Marys at 26.9 days.
- West Mifflin, PA 5 mi, 8.8 days
- Whitehall, PA 5 mi, 8.8 days
- Bethel Park, PA 5 mi, 11.6 days
- Baldwin, PA 6 mi, 8.8 days
- McKeesport, PA 6 mi, 8.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Donora 1 SW, 10.0 miles from Jefferson Hills. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.