MELBOURNE — Maria Sharapova was already soaking in ice by the time the extreme weather warning arrived. It seemed bafflingly late to the four-time major winner, who felt fried after playing for 3½ hours in searing heat to reach the third round of the Australian Open. She didn't know it when she was out on Rod Laver Arena tangling with Karin Knapp on Thursday, but tournament organizers had finally conceded it was unsafe to keep players on court on the third consecutive day of what is shaping as a once-in-a-century heat wave.