Ice dam risk in Marion, OH
How often ice dams form in Marion
11.5 dam days a winter
Moderate risk. On an ordinary house in Marion, conditions for an ice dam come on about 11.5 days in a normal winter, mostly in January and February.
Marion averages 24 inches of snow a year and about 38 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 Marion
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.9 | Moderate |
| Typical, some insulation, not air-sealed | 11.5 | Moderate |
| Older or poorly insulated, warm attic | 18.4 | High |
Sealing and insulating a typical attic takes out about 5.6 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 18.4 days.
Preventing ice dams on a Marion 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.
Which to spend on first: air sealing or heat cable.
Marion winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 7.6 | 14.0 | 4.8 |
| February | 6.6 | 11.8 | 3.7 |
| March | 4.1 | 3.9 | 0.8 |
| April | 0.4 | 0.0 | 0.0 |
| November | 0.6 | 0.5 | 0.1 |
| December | 4.5 | 7.5 | 2.1 |
Marion next to nearby towns
Marion ranks 85 of 176 Ohio cities here for ice-dam days, behind Euclid at 24.8 days.
- Bucyrus, OH 16 mi, 13.9 days
- Galion, OH 20 mi, 13.8 days
- Delaware, OH 22 mi, 10.4 days
- Marysville, OH 29 mi, 10.4 days
- Powell, OH 30 mi, 6.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Marion 2 N, 1.3 miles from Marion. 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.