Firefighters went on alert as the mercury crept towards an expected maximum of 44 degrees Celsius (111 F), the highest since Black Saturday bushfires in 2009 that killed about 180 people in the southeastern state of Victoria.
"Glam Slam and Australian Tennis Championships matches have been suspended on all outside courts at Melbourne Park and Albert Reserve," tournament organisers said on social media.
It was the second day that heat had affected play, after the roof at the Rod Laver arena was closed on Thursday for the women's semi finals match.
But the blistering heat did not stop the world No. 4, Japan's Naomi Osaka, from taking to the practice courts early, ahead of Saturday's women's final, where she faces the world number 6, the Czech Petra Kvitova.
Crowds were only expected to gather later in the day for the men's semi finals between world No. 1 Novak Djokovic, and Lucas Pouille of France, ranked 31.
Fire officials in the state's north set the danger rating to "extreme," while bushfires raging out of control around eastern Timbarra prompted an emergency warning to campers.
In the southern island state of Tasmania, officials issued eight emergency warnings.
"We've got a lot of fire in the landscape," state fire official Andrew McGuinness told broadcaster ABC. "Some of those fires are quite large. And already, we're seeing quite nasty fire weather conditions."
In Victoria, home to 4 million people, rolling power outages of two hours each could hit about 60,000 homes, after blackouts on Thursday in Adelaide, the capital of South Australia, which saw temperatures hit 46.2 C (115.16 F), surpassing a record set in 1939.
Australia's power operator again ordered industrial users to ease back and reduce pressure on Victoria's overburdened grid, including an aluminium smelter owned by Alcoa in the town of Portland.
Only a few people sat under the umbrellas outside Melbourne cafes that are usually heaving by midday, while ice cream melted slowly in the open-air store front of a Ben and Jerry’s that had no customers.
Still, some businesses were banking on more patrons as temperatures cool ahead of a long weekend anchored by Saturday's national holiday, Australia Day.
"Days like this attract more customers for us," said Charlotte Jobling, of the Ice Bar in the trendy Fitzroy district.
"Although the streets are a bit quieter, people who are out and about are more likely to come inside. We are hopeful for a full-on evening tonight."
(Reporting by Melanie Burton and Sonali Paul in MELBOURNE; Editing by Clarence Fernandez)
