When a New Yorker looks like he has a suntan, it's probably rust.
As far as informing the headmaster, Harry had no idea where Dumbledore went during the summer holidays. He amused himself for a moment, picturing Dumbledore, with his long silver beard, full-length wizard's robes, and pointed hat, stretched out on a beach somewhere, rubbing suntan lotion onto his long crooked nose.
Never bet with anyone you meet on the first tee who has a deep suntan, a 1-iron in his bag, and squinty eyes.
Who doesn't feel studious when he doesn't have a girl with a Riviera suntan?