When hail strikes an asphalt shingle, the granules are knocked loose and knocked off as well as driven into the matting of the shingle itself. At the same time, the fiberglass matting on which asphalt is laid before applying the granules during the manufacturing process, gets fractured/torn. Depending on the size of the hail and the condition of the shingles, the fractures may be small or large. Even with smaller fractures, over time the exposure to UV sun rays and temperature variation particularly in the winter, small fractures develop into leaks over time.