Christmas was coming. One morning in mid-December, Hogwarts woke to find
itself covered in several feet of snow. The lake froze solid and the
Weasley twins were punished for bewitching several snowballs so that
they followed Quirrell around, bouncing off the back of his turban. The
few owls that managed to battle their way through the stormy sky to
deliver mail had to be nursed back to health by Hagrid before they could
fly off again.