Ice dam risk in Newton, MA
Ice dams in Newton, MA: how often
16.0 dam days a winter
High risk. On an ordinary house in Newton, conditions for an ice dam come on about 16.0 days in a normal winter, mostly in January and February.
Newton averages 46 inches of snow a year and about 56 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 Newton
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 10.2 | Moderate |
| Typical, some insulation, not air-sealed | 16.0 | High |
| Older or poorly insulated, warm attic | 23.4 | High |
Sealing and insulating a typical attic takes out about 5.9 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 23.4 days.
What to do about ice dams in Newton
- 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.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
Which to spend on first: air sealing or heat cable.
Newton winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 13.8 | 16.8 | 5.7 |
| February | 8.9 | 15.6 | 4.9 |
| March | 8.2 | 12.1 | 2.7 |
| April | 2.2 | 1.2 | 0.1 |
| November | 1.1 | 1.2 | 0.2 |
| December | 11.5 | 9.2 | 2.5 |
Newton next to nearby towns
Newton ranks 20 of 58 Massachusetts cities here for ice-dam days, behind Pittsfield at 31.3 days.
- Watertown, MA 3 mi, 14.8 days
- Waltham, MA 4 mi, 18.8 days
- Cambridge, MA 6 mi, 13.7 days
- Somerville, MA 7 mi, 13.7 days
- Medford, MA 8 mi, 13.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Natick, 7.7 miles from Newton. 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.