Ice dam risk in Ontario, CA
Ice dams in Ontario, CA: how often
0.0 dam days a winter
Almost never. An ordinary house in Ontario sees 0.0 days a winter when an ice dam can form, because snow rarely stays on a roof long enough below freezing.
Ontario averages 0 inches of snow a year and about 0 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 Ontario?
- 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.
Ontario next to nearby towns
Ontario ranks 30 of 376 California cities here for ice-dam days, behind Truckee at 36.3 days.
- Eastvale, CA 5 mi, 0.0 days
- Chino, CA 6 mi, 0.0 days
- Montclair, CA 6 mi, 0.0 days
- Upland, CA 6 mi, 0.0 days
- Rancho Cucamonga, CA 7 mi, 0.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Pomona/Fairplex, 9.7 miles from Ontario. 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.