Third seed Maria Sharapova survived a desperate struggle against Karin Knapp as the Australian Open continued to boil.
The pair were on court for three hours and 28 minutes in temperatures that reached 42.4C before Sharapova finally came through 6-3 4-6 10-8 to book her place in the third round against France's Alize Cornet.
The temperature was already approaching 40C when the match began at 11am and the seats on Rod Laver Arena not in the shade were virtually empty.
Sharapova, who missed the end of last season with a shoulder problem, initially struggled with her serve and a series of double faults helped Knapp break to lead 2-1.
That was as good as it got for the 44th-ranked Italian in the first set, though, as Sharapova reeled off four games in a row to take control.
The Russian was wearing an ice vest at changes of ends to try to keep cool but she condemned herself to a third set with a sloppy service game at 4-5 to lose the second.
Both players headed off court for the 10-minute break between second and third sets allowed for women under the tournament's extreme heat policy.
Knapp returned to the court carrying two bags of ice and, although Sharapova broke serve in the first game, the third seed cast despairing looks towards new coach Sven Groeneveld when she was broken straight back.
The volume of the Sharapova shriek was going up and up, but she forged ahead again with another break to lead 2-1.
The 26-year-old is no stranger to long matches under the Melbourne sun, including an infamous tussle with Camille Pin in 2007, after which she said she had been delusional because of the conditions.
Fighting spirit has never been a deficiency for Sharapova, though, and, although Knapp levelled once more at 3-3, Sharapova went ahead again.
The Russian was less than impressed to be given a time violation for taking too long between points, and her day did not get any better.
She had three match points at 5-4 but Knapp saved all of them and then broke with the luckiest of net cords.
Although the extreme heat policy had now been fully implemented, the rule requires players to finish the set they are playing before play is suspended, meaning it was no help at all to Sharapova.
On and on they went, until finally the third seed broke to lead 9-8 having been two points from defeat a game earlier.
And, despite 12 double faults and 67 unforced errors in total, Sharapova clinched victory on her fourth match point when Knapp blasted a backhand long.
Referring to the Pin match, she said in her courtside interview: "I remember being really close to passing out but I'm feeling much better now, I think you just get numb to it.
"Recovery's going to be extremely important but these are the matches you work for and I'm happy to get through."