Ice dam risk in Rosemount, MN
Will your roof get ice dams in Rosemount, MN?
32.6 dam days a winter
High risk. On an ordinary house in Rosemount, conditions for an ice dam come on about 32.6 days in a normal winter, mostly in January and February.
Rosemount averages 41 inches of snow a year and about 90 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 Rosemount
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 13.0 | Moderate |
| Typical, some insulation, not air-sealed | 32.6 | High |
| Older or poorly insulated, warm attic | 57.2 | Severe |
Sealing and insulating a typical attic takes out about 19.7 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 57.2 days.
Preventing ice dams on a Rosemount 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.
Rosemount winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.5 | 25.7 | 11.2 |
| February | 6.4 | 22.0 | 8.3 |
| March | 8.0 | 13.3 | 3.2 |
| April | 1.8 | 2.0 | 0.2 |
| October | 0.3 | 0.1 | 0.0 |
| November | 7.0 | 5.6 | 1.3 |
| December | 7.0 | 20.9 | 8.4 |
Rosemount next to nearby towns
Rosemount ranks 63 of 103 Minnesota cities here for ice-dam days, behind Hermantown at 52.9 days.
- Inver Grove Heights, MN 6 mi, 32.4 days
- Apple Valley, MN 6 mi, 32.6 days
- Eagan, MN 7 mi, 32.4 days
- Farmington, MN 8 mi, 32.6 days
- Cottage Grove, MN 9 mi, 32.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Farmington 3NW, 7.6 miles from Rosemount. 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.