Ice dam risk in Fargo, ND
Will your roof get ice dams in Fargo, ND?
43.6 dam days a winter
Severe risk. On an ordinary house in Fargo, conditions for an ice dam come on about 43.6 days in a normal winter, mostly in January and February.
Fargo averages 53 inches of snow a year and about 110 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 Fargo
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 14.9 | Moderate |
| Typical, some insulation, not air-sealed | 43.6 | Severe |
| Older or poorly insulated, warm attic | 79.5 | Severe |
Sealing and insulating a typical attic takes out about 28.7 days a winter here. It drops the risk from severe to moderate. An older house with a warm attic should expect closer to 79.5 days.
Preventing ice dams on a Fargo 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.
Fargo winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 12.2 | 29.1 | 13.5 |
| February | 7.7 | 26.2 | 11.2 |
| March | 9.3 | 18.1 | 5.4 |
| April | 4.0 | 3.2 | 0.4 |
| October | 0.7 | 0.2 | 0.0 |
| November | 8.0 | 10.2 | 3.2 |
| December | 10.8 | 22.7 | 9.9 |
Fargo next to nearby towns
Fargo ranks 3 of 9 North Dakota cities here for ice-dam days, behind Jamestown at 45.7 days.
- West Fargo, ND 4 mi, 41.7 days
- Moorhead, MN 4 mi, 43.6 days
- Detroit Lakes, MN 47 mi, 46.7 days
- Fergus Falls, MN 54 mi, 47.3 days
- Grand Forks, ND 74 mi, 44.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Moorhead, 4.1 miles from Fargo. 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.