Ice dam risk in Amherst, OH
How often ice dams form in Amherst
15.3 dam days a winter
High risk. On an ordinary house in Amherst, conditions for an ice dam come on about 15.3 days in a normal winter, mostly in January and February.
Amherst averages 47 inches of snow a year and about 52 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
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 7.9 | Moderate |
| Typical, some insulation, not air-sealed | 15.3 | High |
| Older or poorly insulated, warm attic | 24.6 | High |
Sealing and insulating a typical attic takes out about 7.4 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 24.6 days.
Preventing ice dams on a Amherst 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 winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 14.4 | 18.1 | 6.1 |
| February | 12.4 | 14.8 | 4.7 |
| March | 8.4 | 6.8 | 1.5 |
| April | 1.9 | 0.7 | 0.1 |
| November | 1.4 | 1.8 | 0.3 |
| December | 8.5 | 10.0 | 2.8 |
Amherst next to nearby towns
Amherst ranks 19 of 176 Ohio cities here for ice-dam days, behind Euclid at 24.8 days.
- Lorain, OH 4 mi, 11.3 days
- Vermilion, OH 4 mi, 15.3 days
- Elyria, OH 7 mi, 11.3 days
- North Ridgeville, OH 11 mi, 11.3 days
- Avon, OH 12 mi, 11.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Oberlin, 8.7 miles from Amherst. 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.