Play should have been halted at the Sydney International due to the sweltering heat, women's top seed Agnieszka Radwanska said after she beat Japan's Kimiko Date-Krumm 6-4 6-3 on Tuesday to advance to the quarter-finals.
The world number four, who was given a bye into the second round, played the opening match on centre court as temperatures in Australia's largest city exceeded 40 Celsius.
"I think this is too hot to play tennis," Radwanska told reporters. "Even for players, for ball kids, for the people sitting out there, I think it's just too hot."
Sydney was expected to hit a maximum of 43C on Tuesday as Australia swelters in a heatwave that has sparked raging bush fires.
The Australian Bureau of Meteorology reported a temperature high of 41.1 C at 1339 (local) at Sydney's Olympic Park.
Warm northwest winds had been expected to increase on-court temperatures closer to 50 and officials provided shading, ice towels and additional drinks for the players, while staff would work shorter shifts to try to mitigate the effects of the heat.
"When I was warming up at 9:30 (2030 GMT) it was still okay, but during our match it was pretty hot, especially in the end of the match it was getting worse and worse," the 23-year-old Pole added.
"Today was one of the hottest day I (have) played for sure."
Former French Open champion Li Na, who followed Radwanska on to court, compared the heat to playing in a sauna, but she was good enough to speed through Japan's Ayumi Morita 6-1 6-0 in 52 minutes.
"I was feeling, I don't know, just feeling like unbelievable. They say it was 40, but even on the tennis court even more," Li said.
"I mean, even didn't finish the match, just finish (the) first set (and) I was feeling my feet already burning."
World number 12 Juan Monaco and 19 Kei Nishikori's final Australian Open preparations were also in doubt with the Argentine withdrawing on Tuesday from the invitational Kooyong tournament in Melbourne with a hand injury.
"I had a phone call from Juan Monaco's management this morning which indicated to me that he had a hand injury," tournament director Colin Stubs told reporters.
"They're not certain how serious it is but he has been advised by his doctor not to play in the next few days with the hope that he can take his place in the Australian Open."
The Argentine's spot in the eight man tournament, which starts on Wednesday, was taken by Paul-Henri Mathieu, Stubs said.
Japan's Nishikori also told reporters at the club in a leafy suburb close to Melbourne's central city the knee injury that forced him out of the semi-finals in Brisbane on Saturday was still causing him problems and he did not know if he would play at Kooyong.
"I don't know," he said when asked if whether he could play. "I'm going to try to hit today and let's see how it goes.
"It's not bad. Let's cross the fingers and hopefully it will be okay."