Ice dams are common wherever roofs can receive heavy snow buildups.
Snow acts like an insulation layer on the roof above the attic.
If the home lacks proper attic ventilation and has inadequate ceiling insulation, the temperature in the attic rises. Ice dams occur when snow melts on the roof above the warmed attic and water from the melting refreezes at the colder roof edge and soffit. As the ice dam builds, water from the melting snow begins to pool behind it and can eventually work up under the shingles and enter the attic. This can cause damage to the roof, ceilings, walls, and contents of the home. When the ceiling insulation becomes wet, it loses its insulation value, which can make the attic even warmer and make the ice dam condition worse.