Ice dam risk in Sunnyside, WA
Will your roof get ice dams in Sunnyside, WA?
5.5 dam days a winter
Moderate risk. On an ordinary house in Sunnyside, conditions for an ice dam come on about 5.5 days in a normal winter, mostly in January and December.
Sunnyside averages 10 inches of snow a year and about 20 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 Sunnyside
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.5 | Low |
| Typical, some insulation, not air-sealed | 5.5 | Moderate |
| Older or poorly insulated, warm attic | 8.0 | Moderate |
Sealing and insulating a typical attic takes out about 2.0 days a winter here. It drops the risk from moderate to low.
Preventing ice dams on a Sunnyside roof
- 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.
Sunnyside winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 3.2 | 8.7 | 2.5 |
| February | 1.2 | 2.3 | 0.5 |
| March | 0.4 | 0.3 | 0.0 |
| November | 1.7 | 1.2 | 0.2 |
| December | 3.4 | 7.2 | 2.2 |
Sunnyside next to nearby towns
Sunnyside ranks 12 of 91 Washington cities here for ice-dam days, behind Spokane at 13.0 days.
- Grandview, WA 7 mi, 5.5 days
- West Richland, WA 29 mi, 0.3 days
- Yakima, WA 32 mi, 6.9 days
- Richland, WA 34 mi, 0.3 days
- Kennewick, WA 40 mi, 0.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Moxee City 10 E, 15.2 miles from Sunnyside. 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.