Ice dam risk in Post Falls, ID
Will your roof get ice dams in Post Falls, ID?
13.1 dam days a winter
Moderate risk. On an ordinary house in Post Falls, conditions for an ice dam come on about 13.1 days in a normal winter, mostly in January and December.
Post Falls averages 27 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 Post Falls
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.2 | Moderate |
| Typical, some insulation, not air-sealed | 13.1 | Moderate |
| Older or poorly insulated, warm attic | 18.0 | High |
Sealing and insulating a typical attic takes out about 3.9 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 18.0 days.
Preventing ice dams on a Post Falls 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.
Post Falls winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.7 | 15.9 | 4.7 |
| February | 3.2 | 10.2 | 2.6 |
| March | 1.8 | 3.9 | 0.8 |
| November | 1.4 | 4.4 | 0.9 |
| December | 12.1 | 13.2 | 4.0 |
Post Falls next to nearby towns
Post Falls ranks 12 of 26 Idaho cities here for ice-dam days, behind Rexburg at 42.8 days.
- Rathdrum, ID 5 mi, 13.1 days
- Coeur d'Alene, ID 7 mi, 16.7 days
- Hayden, ID 7 mi, 16.7 days
- Liberty Lake, WA 8 mi, 13.0 days
- Spokane Valley, WA 14 mi, 13.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Bayview Model Basin, 25.1 miles from Post Falls. 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.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.
- The weather station is 25 miles away, far enough that local snow can differ.