Ice dam risk in Muskego, WI
Ice dams in Muskego, WI: how often
21.4 dam days a winter
High risk. On an ordinary house in Muskego, conditions for an ice dam come on about 21.4 days in a normal winter, mostly in January and February.
Muskego averages 37 inches of snow a year and about 62 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 Muskego
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.4 | Moderate |
| Typical, some insulation, not air-sealed | 21.4 | High |
| Older or poorly insulated, warm attic | 36.3 | Severe |
Sealing and insulating a typical attic takes out about 11.9 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 36.3 days.
What to do about ice dams in Muskego
- 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.
Muskego winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.4 | 19.9 | 8.0 |
| February | 10.1 | 19.4 | 6.9 |
| March | 4.6 | 7.6 | 1.8 |
| April | 1.1 | 0.6 | 0.0 |
| October | 0.1 | 0.1 | 0.0 |
| November | 1.8 | 2.1 | 0.4 |
| December | 8.8 | 12.3 | 4.2 |
Muskego next to nearby towns
Muskego ranks 70 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Franklin, WI 6 mi, 18.4 days
- New Berlin, WI 7 mi, 21.4 days
- Greendale, WI 8 mi, 18.4 days
- Greenfield, WI 9 mi, 18.9 days
- West Allis, WI 11 mi, 18.9 days
Where these numbers come from
NOAA 1991–2020 climate normals from Waukesha Wwtp, 10.7 miles from Muskego. 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.