Ice dam risk in Worthington, MN
Will your roof get ice dams in Worthington, MN?
34.3 dam days a winter
High risk. On an ordinary house in Worthington, conditions for an ice dam come on about 34.3 days in a normal winter, mostly in January and February.
Worthington averages 45 inches of snow a year and about 93 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 Worthington
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 13.7 | Moderate |
| Typical, some insulation, not air-sealed | 34.3 | High |
| Older or poorly insulated, warm attic | 60.0 | Severe |
Sealing and insulating a typical attic takes out about 20.6 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 60.0 days.
What to do about ice dams in Worthington
- 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.
Worthington winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.8 | 25.1 | 10.9 |
| February | 10.9 | 22.1 | 8.8 |
| March | 5.7 | 14.5 | 4.2 |
| April | 4.4 | 3.0 | 0.4 |
| May | 0.2 | 0.1 | 0.0 |
| October | 1.0 | 0.6 | 0.1 |
| November | 4.6 | 7.3 | 1.9 |
| December | 8.6 | 20.1 | 8.1 |
Worthington next to nearby towns
Worthington ranks 50 of 103 Minnesota cities here for ice-dam days, behind Hermantown at 52.9 days.
- Spencer, IA 40 mi, 27.3 days
- Brandon, SD 49 mi, 25.5 days
- Fairmont, MN 57 mi, 30.3 days
- Sioux Falls, SD 57 mi, 25.5 days
- Harrisburg, SD 57 mi, 26.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Worthington 2 NNE, 1.5 miles from Worthington. 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.