Ice dam risk in Grand Haven, MI
How often ice dams form in Grand Haven
22.2 dam days a winter
High risk. On an ordinary house in Grand Haven, conditions for an ice dam come on about 22.2 days in a normal winter, mostly in January and February.
Grand Haven averages 87 inches of snow a year and about 74 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 Grand Haven
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 10.9 | Moderate |
| Typical, some insulation, not air-sealed | 22.2 | High |
| Older or poorly insulated, warm attic | 36.4 | Severe |
Sealing and insulating a typical attic takes out about 11.3 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 36.4 days.
Preventing ice dams on a Grand Haven 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.
Grand Haven winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 29.1 | 23.5 | 8.3 |
| February | 20.0 | 20.0 | 6.7 |
| March | 7.5 | 10.1 | 2.2 |
| April | 1.8 | 0.9 | 0.1 |
| November | 6.5 | 3.9 | 0.5 |
| December | 22.3 | 15.5 | 4.3 |
Grand Haven next to nearby towns
Grand Haven ranks 18 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- Norton Shores, MI 8 mi, 22.2 days
- Muskegon, MI 12 mi, 22.2 days
- Holland, MI 21 mi, 22.4 days
- Walker, MI 24 mi, 22.4 days
- Grandville, MI 26 mi, 22.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Muskegon County Airport, 8.1 miles from Grand Haven. 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.