Ice dam risk in Amherst Town, MA
How often ice dams form in Amherst Town
15.9 dam days a winter
High risk. On an ordinary house in Amherst Town, conditions for an ice dam come on about 15.9 days in a normal winter, mostly in January and February.
Amherst Town averages 37 inches of snow a year and about 54 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 Amherst Town
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 10.0 | Moderate |
| Typical, some insulation, not air-sealed | 15.9 | High |
| Older or poorly insulated, warm attic | 23.2 | 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 23.2 days.
Preventing ice dams on a Amherst Town roof
- 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.
Amherst Town winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.1 | 16.6 | 5.6 |
| February | 11.0 | 16.6 | 5.2 |
| March | 7.3 | 9.4 | 2.1 |
| April | 1.0 | 0.5 | 0.1 |
| November | 1.6 | 1.2 | 0.2 |
| December | 7.5 | 9.9 | 2.7 |
Amherst Town next to nearby towns
Amherst Town ranks 21 of 58 Massachusetts cities here for ice-dam days, behind Pittsfield at 31.3 days.
- Northampton, MA 9 mi, 15.9 days
- Easthampton, MA 11 mi, 15.9 days
- Holyoke, MA 13 mi, 15.9 days
- Chicopee, MA 13 mi, 16.4 days
- Palmer Town, MA 16 mi, 18.9 days
Where these numbers come from
NOAA 1991–2020 climate normals from Amherst, 2.2 miles from Amherst Town. 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.