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

https://beauspvl311.almoheet-travel.com/how-winter-ice-dams-leak-into-seattle-homes

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.