Ice damming is a common issue in late winter and early spring. Common causes are poor attic venting and/or poor sealing and insulation to house.
This picture is from a newer addition with poor attic space ventilation and a low slope roof. The heat is escaping near the wall melting the snow which then freezes as the water runs down the roof slope and refreezes at the eaves. Note the icicles and the block of ice near center of window.
