Ice dam risk in St. Paul, MN
Will your roof get ice dams in St. Paul, MN?
22.8 dam days a winter
High risk. On an ordinary house in St. Paul, conditions for an ice dam come on about 22.8 days in a normal winter, mostly in January and February.
St. Paul averages 40 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 St. Paul
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.9 | Moderate |
| Typical, some insulation, not air-sealed | 22.8 | High |
| Older or poorly insulated, warm attic | 40.2 | Severe |
Sealing and insulating a typical attic takes out about 13.9 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 40.2 days.
What to do about ice dams in St. Paul
- 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.
St. Paul winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.3 | 19.6 | 8.5 |
| February | 12.3 | 16.4 | 6.4 |
| March | 4.0 | 9.1 | 2.3 |
| April | 2.1 | 1.7 | 0.2 |
| October | 0.5 | 0.4 | 0.0 |
| November | 3.0 | 2.5 | 0.6 |
| December | 10.2 | 12.2 | 4.8 |
St. Paul next to nearby towns
St. Paul ranks 88 of 103 Minnesota cities here for ice-dam days, behind Hermantown at 52.9 days.
- West St. Paul, MN 3 mi, 32.4 days
- Mendota Heights, MN 5 mi, 32.4 days
- Roseville, MN 5 mi, 22.8 days
- South St. Paul, MN 5 mi, 32.4 days
- Little Canada, MN 5 mi, 22.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from U Of Mn St Paul, 4.7 miles from St. Paul. 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.