In some rare instances, curling can reveal itself only under cold weather conditions. This would be referred to as winter curling. The corners of the shingles will slightly curl up from the roof deck when cold, then lay flat again during warmer weather. This is prevalent during damp winter conditions when frost forms on the top surface of the shingles. Cooling on the top surface will cause the shingle to contract while, at the same time, the underside of the shingle in contact with the roof receives a certain amount of radiant heat from the attic space. The variance in temperature between the top side and underside of the shingle will result in some minor curling. This does not affect the shingle's durability and performance.