Play will start 30 minutes earlier at the Australian Open on Saturday with temperatures set to reach 40C in Melbourne.
Play will begin on all courts at 10:30 local time (23:30 GMT) instead of the usual 11:00 start.
The Australian Bureau of Meteorology has issued a severe heatwave warning in Melbourne and the state of Victoria.
Play will be suspended at the Australian Open if the tournament’s heat stress scale hits its maximum of five.
“It’s not a lot of fun playing in those temperatures,” said American men’s 19th seed Tommy Paul.
The scale measures four factors: radiant heat (or the strength of the sun), air temperature in the shade, relative humidity and wind speed.
If a five is recorded on the heat stress scale, matches on Rod Laver Arena, Margaret Court Arena and John Cain Arena will stop to allow the roof to be closed before play can continue.
Defending women’s champion Madison Keys and Czech former world number one Karolina Pliskova open play on Laver, followed by defending champion Jannik Sinner.
Another American seed, Jessica Pegula, and Italian men’s fifth seed Lorenzo Musetti are among the early starters on Court and Cain.
“I wouldn’t like to play the match because I think it’s too much on our bodies. I’m glad that at least we have a heat rule,” world number one Aryna Sabalenka said.
