“An intense cold swept over them all. Harry felt his own breath catch in his chest. The cold went deeper than his skin. It was inside his chest, it was inside his very heart. . . .
Harry’s eyes rolled up into his head. He couldn’t see. He was drowning in cold. There was a rushing in his ears as though of water. He was being dragged downward, the roaring growing louder . . .
_Harry Potter and the Prisoner of Azkaban