Ice dam risk in Portland, OR
Ice dams in Portland, OR: how often
0.1 dam days a winter
Almost never. An ordinary house in Portland sees 0.1 days a winter when an ice dam can form, because snow rarely stays on a roof long enough below freezing.
Portland averages 4 inches of snow a year and about 2 days with snow on the ground. Too little lies on the roof for long. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
Do you need to do anything in Portland?
- Nothing for ice dams. If you are buying here and an inspector mentions water at the eaves, ask what they saw: it is far more likely a gutter, flashing or drip-edge problem than ice.
Snowy places are not always the worst: why snowfall misleads.
Portland winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 1.3 | 0.6 | 0.0 |
| February | 1.4 | 0.7 | 0.0 |
| December | 0.9 | 0.3 | 0.0 |
Portland next to nearby towns
Portland ranks 22 of 57 Oregon cities here for ice-dam days, behind Klamath Falls at 9.8 days.
- Milwaukie, OR 7 mi, 0.1 days
- Vancouver, WA 7 mi, 0.2 days
- Lake Oswego, OR 9 mi, 0.1 days
- Beaverton, OR 9 mi, 0.1 days
- Happy Valley, OR 10 mi, 0.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Portland Kgw-Tv, 2.3 miles from Portland. 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.