Ice dam risk in Newburyport, MA
How often ice dams form in Newburyport
20.7 dam days a winter
High risk. On an ordinary house in Newburyport, conditions for an ice dam come on about 20.7 days in a normal winter, mostly in January and February.
Newburyport averages 67 inches of snow a year and about 75 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. 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 Newburyport
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 13.4 | Moderate |
| Typical, some insulation, not air-sealed | 20.7 | High |
| Older or poorly insulated, warm attic | 29.7 | High |
Sealing and insulating a typical attic takes out about 7.2 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 29.7 days.
What to do about ice dams in Newburyport
- 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.
Newburyport winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 17.9 | 21.4 | 7.1 |
| February | 17.2 | 20.7 | 6.3 |
| March | 14.4 | 16.2 | 3.5 |
| April | 2.4 | 2.0 | 0.2 |
| October | 0.4 | 0.2 | 0.0 |
| November | 1.8 | 1.8 | 0.3 |
| December | 13.0 | 12.3 | 3.3 |
Newburyport next to nearby towns
Newburyport ranks 7 of 58 Massachusetts cities here for ice-dam days, behind Pittsfield at 31.3 days.
- Amesbury, MA 4 mi, 20.5 days
- Haverhill, MA 10 mi, 20.5 days
- Methuen, MA 16 mi, 20.5 days
- Lawrence, MA 16 mi, 20.5 days
- Gloucester, MA 16 mi, 12.5 days
Where these numbers come from
NOAA 1991–2020 climate normals from Groveland, 9.1 miles from Newburyport. 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.