Ice dam risk in Pocatello, ID
Ice dams in Pocatello, ID: how often
9.4 dam days a winter
Moderate risk. On an ordinary house in Pocatello, conditions for an ice dam come on about 9.4 days in a normal winter, mostly in December and January.
Pocatello averages 30 inches of snow a year and about 35 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 Pocatello
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.9 | Moderate |
| Typical, some insulation, not air-sealed | 9.4 | Moderate |
| Older or poorly insulated, warm attic | 13.9 | Moderate |
Sealing and insulating a typical attic takes out about 3.6 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 13.9 days.
Preventing ice dams on a Pocatello 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.
Which to spend on first: air sealing or heat cable.
Pocatello winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.5 | 10.8 | 3.2 |
| February | 6.7 | 7.3 | 1.8 |
| March | 3.3 | 1.8 | 0.3 |
| April | 1.4 | 0.2 | 0.0 |
| May | 0.2 | 0.1 | 0.0 |
| October | 0.6 | 0.4 | 0.0 |
| November | 2.9 | 2.1 | 0.4 |
| December | 9.1 | 12.5 | 3.8 |
Pocatello next to nearby towns
Pocatello ranks 15 of 26 Idaho cities here for ice-dam days, behind Rexburg at 42.8 days.
- Chubbuck, ID 4 mi, 20.8 days
- Blackfoot, ID 23 mi, 20.1 days
- Idaho Falls, ID 48 mi, 36.4 days
- Ammon, ID 49 mi, 36.4 days
- Burley, ID 71 mi, 3.1 days
Where these numbers come from
NOAA 1991–2020 climate normals from Pocatello City, 0.8 miles from Pocatello. 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.