Ice dams in Seattle form when warm attics melt snow that refreezes at eaves, forcing water under shingles

https://zanderffcm631.theglensecret.com/the-real-cost-of-delaying-a-seattle-roof-replacement

Ice dams in Seattle form when warm attics melt snow that refreezes at eaves, forcing water under shingles. Continuous soffit-to-ridge ventilation, air sealing, and eave ice-and-water shield stop hidden winter leaks.