High temperatures disrupts tennis at Australian Open in Melbourne
Organizers of the grand slam event said Thursday that they had issued an "extreme heat policy" after temperatures rose above 40 degrees Celsius (104 degrees Fahrenheit).
That means that matches already under way on court will be suspended at the end of the set being played.
The organizers said the roof would be closed at Rod Laver Arena and Hisense Arena so that players could continue their matches on those courts.
But new matches won't start on outdoor courts "until the temperature falls back down to a temperature deemed fit for play by the tournament director," the statement on the website said.
The severe heat at Melbourne Park this week has already caused problems for players.
Canadian Frank Dancevic fainted during his defeat in the first round on Tuesday. He said he thought the conditions were "inhumane."
And it's not just players who have succumbed to the elements. One of the ball boys fainted during 11th-seed Milos Raonic's four-set victory over Spain's Daniel Gimeno-Traver on Tuesday.