Jelena Jankovic said her head felt like it was about to explode, Li Na described conditions as sauna-like and Agnieszka Radwanska declared it simply "too hot to play".
But in temperatures that reached 41.4 degrees at Sydney Olympic Park, play tennis they did - right throughout the day, only pausing when women's matches went to a third set for a 10 minute break.
"It's like 40 degrees but on court it feels like 50 - it feels so hot," said former world No 1 Jankovic, who went down to Roberta Vinci 3-6 6-4 7-6 (7-4).
"Then the feet are burning; my head was like going to explode there."
The end result was better for top seed Radwanska, the Pole claiming a 6-4 6-3 win over Kimiko Date-Krumm to reach the last eight and remain unbeaten in 2013 after winning the Auckland tournament last week.
"I think this is too hot to play tennis," Radwanska said when asked if matches should be put on hold.
"I think I would prefer to go on court at 11pm and play a match."
Galina Voskoboeva did suffer from heat stress in her match against second seed Angelique Kerber and had to take a medical time out.
Kerber, who rocketed from No 32 to No 5 in the world in 2012 and defeated Voskoboeva 6-2 7-5 said she hardly noticed what was going on with her opponent.
"For sure the weather conditions are very strong and strange, but I think for everybody it's the same," she said.
"You need to go out there and try your best and just think about the points and not about the weather."
Another former world No 1 in Caroline Wozniacki was more bothered by a hot opponent who could go on to cause some damage at the Australian Open.
Unseeded two-time grand slam winner Svetlana Kuznetsova had an injury-plagued 2012, her ranking blowing out to No 85 in the world, but the Russian suggested her best days were not necessarily behind her with a tidy 7-6 (7-4) 1-6 6-2 win over the Dane.
Italy's Sara Errani moved into the last eight with a 6-1, 6-1 win over Maria Kirilenko and will take on Dominika Cibulkova for a spot in the semi-finals; the Slovakian having a tough three-set win over Ekaterina Makarova.
Samantha Stosur's first round conqueror, Jie Zheng, surrendered meekly after her victory on Monday night, going down 6-0 6-4 to American qualifier Madison Keys.
The weather seemed less of an issue for her countrywoman Li, who beat qualifier Ayumi Morita, in which she only lost one game.