Ice dam risk in Chubbuck, ID
How often ice dams form in Chubbuck
20.8 dam days a winter
High risk. On an ordinary house in Chubbuck, conditions for an ice dam come on about 20.8 days in a normal winter, mostly in January and December.
Chubbuck averages 64 inches of snow a year and about 75 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 Chubbuck
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 13.3 | Moderate |
| Typical, some insulation, not air-sealed | 20.8 | High |
| Older or poorly insulated, warm attic | 30.1 | High |
Sealing and insulating a typical attic takes out about 7.5 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 30.1 days.
Preventing ice dams on a Chubbuck 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.
Chubbuck winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 13.5 | 22.1 | 6.9 |
| February | 10.5 | 17.7 | 4.6 |
| March | 8.1 | 6.1 | 1.0 |
| April | 4.8 | 0.9 | 0.1 |
| May | 0.8 | 0.0 | 0.0 |
| June | 0.1 | 0.0 | 0.0 |
| September | 0.1 | 0.0 | 0.0 |
| October | 2.3 | 0.9 | 0.1 |
| November | 7.0 | 5.8 | 1.2 |
| December | 16.4 | 21.9 | 6.9 |
Chubbuck next to nearby towns
Chubbuck ranks 4 of 26 Idaho cities here for ice-dam days, behind Rexburg at 42.8 days.
- Pocatello, ID 4 mi, 9.4 days
- Blackfoot, ID 19 mi, 20.1 days
- Idaho Falls, ID 44 mi, 36.4 days
- Ammon, ID 45 mi, 36.4 days
- Rexburg, ID 70 mi, 42.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Pocatello 2 NE, 3.5 miles from Chubbuck. 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.