Ice dam risk in Columbia, PA
How often ice dams form in Columbia
6.5 dam days a winter
Moderate risk. On an ordinary house in Columbia, conditions for an ice dam come on about 6.5 days in a normal winter, mostly in February and January.
Columbia averages 23 inches of snow a year and about 28 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 Columbia
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.7 | Low |
| Typical, some insulation, not air-sealed | 6.5 | Moderate |
| Older or poorly insulated, warm attic | 8.7 | Moderate |
The attic matters less in Columbia than in colder towns: there are only 1.8 days a winter between a typical attic and a sealed one.
What to do about ice dams in Columbia
- 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.
More on when a roof rake is worth it.
Columbia winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 7.1 | 8.1 | 2.2 |
| February | 6.7 | 10.2 | 2.5 |
| March | 4.5 | 4.4 | 0.7 |
| April | 0.3 | 0.1 | 0.0 |
| November | 0.7 | 0.4 | 0.1 |
| December | 3.9 | 4.3 | 1.0 |
Columbia next to nearby towns
Columbia ranks 56 of 68 Pennsylvania cities here for ice-dam days, behind St. Marys at 26.9 days.
- Elizabethtown, PA 10 mi, 6.5 days
- Lancaster, PA 10 mi, 5.3 days
- York, PA 13 mi, 5.8 days
- Ephrata, PA 19 mi, 6.4 days
- Lebanon, PA 22 mi, 6.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Landisville 2 NW, 6.9 miles from Columbia. 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.