Have you gone by a home with icicles hanging from the roof? Ice dams are not only are these a physical hazard to any property or people that stand below, it can also cause your roof to leak.
Ice dams or ice damming occurs when warm air escapes from the house through the attic and melts the snow on the roof. The water now runs down the roof freezing at the colder soffits / eaves. Ice then forms preventing further water from draining off the roof that can now seep under any layered roofing system. Reducing heat loss from the home and increasing attic insulation & ventilation will improve ice damming conditions, saving you money & aggravation.