Ice dam risk in Marquette, MI
Will your roof get ice dams in Marquette, MI?
43.6 dam days a winter
Severe risk. On an ordinary house in Marquette, conditions for an ice dam come on about 43.6 days in a normal winter, mostly in January and February.
Marquette averages 102 inches of snow a year and about 125 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. 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 Marquette
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 17.9 | High |
| Typical, some insulation, not air-sealed | 43.6 | Severe |
| Older or poorly insulated, warm attic | 75.8 | Severe |
Sealing and insulating a typical attic takes out about 25.8 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 75.8 days.
Preventing ice dams on a Marquette 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.
- Heat cable is worth pricing here even on a sealed house, along the eave and in the gutters and downspouts it drains into.
Running 60 feet of 5 W/ft cable whenever snow lies below freezing would use about 464 kWh a winter in Marquette, roughly $79 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Marquette winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 25.1 | 30.0 | 13.0 |
| February | 20.9 | 28.4 | 11.4 |
| March | 14.2 | 25.4 | 7.8 |
| April | 8.4 | 8.6 | 1.2 |
| May | 0.3 | 0.2 | 0.0 |
| October | 0.9 | 0.6 | 0.0 |
| November | 11.1 | 9.1 | 1.8 |
| December | 21.1 | 22.6 | 8.3 |
Marquette next to nearby towns
Marquette ranks 2 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- Escanaba, MI 58 mi, 34.4 days
- Marinette, WI 102 mi, 31.3 days
- Suamico, WI 136 mi, 29.3 days
- Howard, WI 141 mi, 29.3 days
- Green Bay, WI 143 mi, 29.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Marquette, 0.9 miles from Marquette. 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.