Ice dam risk in Trenton, NJ
How often ice dams form in Trenton
5.2 dam days a winter
Moderate risk. On an ordinary house in Trenton, conditions for an ice dam come on about 5.2 days in a normal winter, mostly in February and January.
Trenton averages 27 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 Trenton
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.7 | Low |
| Typical, some insulation, not air-sealed | 5.2 | Moderate |
| Older or poorly insulated, warm attic | 7.1 | Moderate |
The attic matters less in Trenton than in colder towns: there are only 1.5 days a winter between a typical attic and a sealed one.
Preventing ice dams on a Trenton roof
- 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.
Trenton winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.2 | 7.6 | 2.0 |
| February | 8.7 | 8.8 | 2.0 |
| March | 4.0 | 4.0 | 0.5 |
| April | 0.5 | 0.1 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 0.5 | 0.1 | 0.0 |
| December | 4.6 | 2.9 | 0.6 |
Trenton next to nearby towns
Trenton ranks 47 of 116 New Jersey cities here for ice-dam days, behind Hopatcong at 14.7 days.
- Princeton, NJ 11 mi, 5.4 days
- Burlington, NJ 11 mi, 5.4 days
- Manville, NJ 24 mi, 6.2 days
- Philadelphia, PA 25 mi, 2.3 days
- New Brunswick, NJ 25 mi, 6.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Trenton-Mercer Airport, 4.6 miles from Trenton. 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.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.