Ice dam risk in Monroe, MI
How often ice dams form in Monroe
14.2 dam days a winter
Moderate risk. On an ordinary house in Monroe, conditions for an ice dam come on about 14.2 days in a normal winter, mostly in February and January.
Monroe averages 41 inches of snow a year and about 48 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 Monroe
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 7.4 | Moderate |
| Typical, some insulation, not air-sealed | 14.2 | Moderate |
| Older or poorly insulated, warm attic | 22.8 | High |
Sealing and insulating a typical attic takes out about 6.8 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 22.8 days.
Preventing ice dams on a Monroe 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.
Monroe winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 12.4 | 14.5 | 5.0 |
| February | 13.5 | 16.6 | 5.4 |
| March | 5.5 | 6.1 | 1.3 |
| April | 0.6 | 0.1 | 0.0 |
| November | 1.0 | 1.1 | 0.1 |
| December | 8.2 | 9.4 | 2.5 |
Monroe next to nearby towns
Monroe ranks 75 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- Flat Rock, MI 14 mi, 14.1 days
- Woodhaven, MI 17 mi, 14.1 days
- Oregon, OH 18 mi, 11.9 days
- Trenton, MI 18 mi, 14.1 days
- Riverview, MI 20 mi, 14.1 days
Where these numbers come from
NOAA 1991–2020 climate normals from Newport 4SSE, 5.8 miles from Monroe. 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.