Ice dam risk in Hermiston, OR
Ice dams in Hermiston, OR: how often
2.6 dam days a winter
Low risk. On an ordinary house in Hermiston, conditions for an ice dam come on about 2.6 days in a normal winter, mostly in January and December.
Hermiston averages 4 inches of snow a year and about 13 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 Hermiston
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 2.0 | Low |
| Typical, some insulation, not air-sealed | 2.6 | Low |
| Older or poorly insulated, warm attic | 3.3 | Low |
The attic matters less in Hermiston than in colder towns: there are only 0.6 days a winter between a typical attic and a sealed one.
What to do about ice dams in Hermiston
- Check the gutters before the first snow and clear them, so meltwater has somewhere to go. If you see icicles thicker than a finger along the eave after a storm, that is the early sign to look at the attic.
Snowy places are not always the worst: why snowfall misleads.
Hermiston winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 1.2 | 4.2 | 0.9 |
| February | 1.4 | 2.6 | 0.5 |
| March | 0.2 | 1.0 | 0.1 |
| October | 0.1 | 0.1 | 0.0 |
| November | 0.0 | 1.3 | 0.2 |
| December | 0.8 | 4.0 | 0.9 |
Hermiston next to nearby towns
Hermiston ranks 9 of 57 Oregon cities here for ice-dam days, behind Klamath Falls at 9.8 days.
- Pendleton, OR 25 mi, 3.1 days
- Kennewick, WA 26 mi, 0.3 days
- Pasco, WA 31 mi, 0.3 days
- Richland, WA 31 mi, 0.3 days
- West Richland, WA 34 mi, 0.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Boardman, 19.7 miles from Hermiston. 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.
- The nearest weather station sits at a noticeably different elevation from Hermiston, so the snow figures may run high or low for the town itself.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.