Temperatures of 40°C are forecast to roast the Australian Open on Saturday, forcing a change of schedule and warnings for fans.
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Play will start in Melbourne at 10:30am on the main arenas, compared to the normal 11am or 11:30am.
Other courts will start match action as early as 10am, with organisers warning spectators to take precautions against the extreme heat and sun.
"We expect pleasant conditions tomorrow morning, in the mid-20s, and will start play earlier and take advantage of the more temperate conditions," tournament director Craig Tiley said.
Novak Djokovic and reigning champions Jannik Sinner and Madison Keys are all scheduled to play on Saturday.
Temperatures are forecast to peak in the late afternoon, but should be back closer to normal for the time of year on Sunday, before rising sharply again to a forecast 43°C on Tuesday.
Three-time runner-up Daniil Medvedev is not in action on Saturday but said the scorching weather could impact his practice for the last 16.
"Worst case, if it's too hot, we can always go indoors. I would prefer outdoors," he said.
He added: "It's going to be interesting to watch on TV. What can I say? Let's see how the guys cope.
"Hopefully no heat stroke and stuff like this."
According to Australian Open rules, the tournament referee can suspend play or order cooling breaks in extreme weather.
Courts with roofs, such as Rod Laver Arena, the centre court, could have their covers closed.