Ice dam risk in Brookings, SD
Will your roof get ice dams in Brookings, SD?
31.5 dam days a winter
High risk. On an ordinary house in Brookings, conditions for an ice dam come on about 31.5 days in a normal winter, mostly in January and December.
Brookings averages 36 inches of snow a year and about 83 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 Brookings
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 12.5 | Moderate |
| Typical, some insulation, not air-sealed | 31.5 | High |
| Older or poorly insulated, warm attic | 55.3 | Severe |
Sealing and insulating a typical attic takes out about 19.0 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 55.3 days.
Preventing ice dams on a Brookings 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.
Brookings winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.5 | 23.7 | 10.4 |
| February | 7.1 | 18.2 | 7.4 |
| March | 6.4 | 12.4 | 3.7 |
| April | 4.1 | 2.5 | 0.4 |
| May | 0.1 | 0.0 | 0.0 |
| October | 1.1 | 0.8 | 0.1 |
| November | 4.7 | 6.6 | 1.9 |
| December | 6.8 | 18.9 | 7.7 |
Brookings next to nearby towns
Brookings ranks 2 of 14 South Dakota cities here for ice-dam days, behind Watertown at 35.4 days.
- Watertown, SD 46 mi, 35.4 days
- Brandon, SD 50 mi, 25.5 days
- Marshall, MN 50 mi, 29.3 days
- Sioux Falls, SD 53 mi, 25.5 days
- Harrisburg, SD 60 mi, 26.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Brookings 2 NE, 1.8 miles from Brookings. 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.