It used to be easier to predict, said Camp. "Before there was easy access to electricity and air-conditioning, everybody knew it was coming. If you were suffering in the heat all night, you"d have your windows open, and you"d feel the cool air. It usually comes through between 04:00 and 07:00, and it was just glorious to have that drop in temperature. We"re less likely to notice it now because we"re in comfort inside our houses with the air-con running."