Ice dam risk in Mechanicsburg, PA
How often ice dams form in Mechanicsburg
8.0 dam days a winter
Moderate risk. On an ordinary house in Mechanicsburg, conditions for an ice dam come on about 8.0 days in a normal winter, mostly in February and January.
Mechanicsburg averages 24 inches of snow a year and about 31 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 Mechanicsburg
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.1 | Moderate |
| Typical, some insulation, not air-sealed | 8.0 | Moderate |
| Older or poorly insulated, warm attic | 11.6 | Moderate |
Sealing and insulating a typical attic takes out about 2.9 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 11.6 days.
Preventing ice dams on a Mechanicsburg 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.
Mechanicsburg winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 6.4 | 10.0 | 3.0 |
| February | 7.7 | 11.5 | 3.2 |
| March | 4.5 | 4.3 | 0.7 |
| April | 0.4 | 0.2 | 0.0 |
| November | 0.7 | 0.4 | 0.0 |
| December | 4.2 | 4.8 | 1.1 |
Mechanicsburg next to nearby towns
Mechanicsburg ranks 44 of 68 Pennsylvania cities here for ice-dam days, behind St. Marys at 26.9 days.
- Harrisburg, PA 8 mi, 8.0 days
- Carlisle, PA 10 mi, 6.9 days
- Elizabethtown, PA 22 mi, 6.5 days
- York, PA 22 mi, 5.8 days
- Hanover, PA 28 mi, 7.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Harrisburg 1 NE, 8.6 miles from Mechanicsburg. 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.