Ice dam risk in Brockton, MA
How often ice dams form in Brockton
7.6 dam days a winter
Moderate risk. On an ordinary house in Brockton, conditions for an ice dam come on about 7.6 days in a normal winter, mostly in January and February.
Brockton averages 34 inches of snow a year and about 30 days with snow on the ground. Plenty falls, but it tends to melt off between storms, which keeps the count lower than the snowfall suggests. That gap is why snowfall alone misleads.
What your attic does to that number in Brockton
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.4 | Moderate |
| Typical, some insulation, not air-sealed | 7.6 | Moderate |
| Older or poorly insulated, warm attic | 10.4 | Moderate |
Sealing and insulating a typical attic takes out about 2.2 days a winter here. It does not move the risk band, but it shortens every dam.
What to do about ice dams in Brockton
- 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.
Which to spend on first: air sealing or heat cable.
Brockton winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.1 | 9.7 | 2.8 |
| February | 12.8 | 9.0 | 2.5 |
| March | 6.9 | 6.1 | 1.2 |
| April | 0.7 | 0.4 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 0.2 | 0.2 | 0.0 |
| December | 4.5 | 4.9 | 1.1 |
Brockton next to nearby towns
Brockton ranks 54 of 58 Massachusetts cities here for ice-dam days, behind Pittsfield at 31.3 days.
- Randolph Town, MA 7 mi, 15.3 days
- Bridgewater Town, MA 8 mi, 7.6 days
- Braintree Town, MA 9 mi, 11.2 days
- Weymouth Town, MA 10 mi, 11.2 days
- Quincy, MA 12 mi, 11.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Brockton, 2.6 miles from Brockton. 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.