Ice dam risk in Harrison, NJ
Ice dams in Harrison, NJ: how often
4.7 dam days a winter
Low risk. On an ordinary house in Harrison, conditions for an ice dam come on about 4.7 days in a normal winter, mostly in February and January.
Harrison averages 28 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 Harrison
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.4 | Low |
| Typical, some insulation, not air-sealed | 4.7 | Low |
| Older or poorly insulated, warm attic | 6.3 | Moderate |
The attic matters less in Harrison than in colder towns: there are only 1.3 days a winter between a typical attic and a sealed one.
What to do about ice dams in Harrison
- Check the gutters before the first snow and clear them, so meltwater has somewhere to go. If you see icicles thicker than a finger along the eave after a storm, that is the early sign to look at the attic.
Snowy places are not always the worst: why snowfall misleads.
Harrison winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.0 | 7.8 | 1.9 |
| February | 8.4 | 8.5 | 1.9 |
| March | 4.7 | 3.4 | 0.4 |
| April | 0.7 | 0.2 | 0.0 |
| October | 0.2 | 0.1 | 0.0 |
| November | 0.3 | 0.2 | 0.0 |
| December | 5.9 | 3.3 | 0.5 |
Harrison next to nearby towns
Harrison ranks 58 of 116 New Jersey cities here for ice-dam days, behind Hopatcong at 14.7 days.
- Newark, NJ 2 mi, 4.7 days
- Kearny, NJ 2 mi, 4.7 days
- North Arlington, NJ 3 mi, 4.7 days
- East Orange, NJ 3 mi, 4.7 days
- Jersey City, NJ 5 mi, 4.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Harrison, 0.4 miles from Harrison. 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.