Ice dam risk in Box Elder, SD
How often ice dams form in Box Elder
13.9 dam days a winter
Moderate risk. On an ordinary house in Box Elder, conditions for an ice dam come on about 13.9 days in a normal winter, mostly in December and January.
Box Elder averages 49 inches of snow a year and about 48 days with snow on the ground. Most of it comes and goes within a few days. 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 Box Elder
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.8 | Moderate |
| Typical, some insulation, not air-sealed | 13.9 | Moderate |
| Older or poorly insulated, warm attic | 20.4 | High |
Sealing and insulating a typical attic takes out about 5.1 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 20.4 days.
What to do about ice dams in Box Elder
- 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.
Which to spend on first: air sealing or heat cable.
Box Elder winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.3 | 10.6 | 3.5 |
| February | 7.7 | 10.1 | 3.2 |
| March | 8.4 | 6.0 | 1.5 |
| April | 10.1 | 4.1 | 0.6 |
| May | 1.5 | 0.3 | 0.0 |
| September | 0.1 | 0.0 | 0.0 |
| October | 3.0 | 1.4 | 0.2 |
| November | 5.7 | 4.3 | 1.1 |
| December | 6.7 | 11.6 | 3.8 |
Box Elder next to nearby towns
Box Elder ranks 13 of 14 South Dakota cities here for ice-dam days, behind Watertown at 35.4 days.
- Rapid City, SD 7 mi, 11.8 days
- Spearfish, SD 45 mi, 17.4 days
- Gillette, WY 120 mi, 18.7 days
- Pierre, SD 138 mi, 21.9 days
- Scottsbluff, NE 158 mi, 11.1 days
Where these numbers come from
NOAA 1991–2020 climate normals from Rapid City Regional Airport, 4.7 miles from Box Elder. 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.