Maria Sharapova survived a scare to reach the Australian Open third round as the temperature exceeded 40C for the third consecutive day in Melbourne.
The 2008 champion edged Karin Knapp 6-3 4-6 10-8 in heat that eventually halted play on outside courts.
Defending champion Victoria Azarenka beat Barbora Zahlavova Strycova 6-2 6-4, while top men's seed Rafael Nadal and Roger Federer won in straight sets.
But Roberto Bautista shocked fifth seed Juan Martin Del Potro in five sets.
The match lasted three hours and 35 minutes, finishing at 01:20 local time with the Spaniard winning 4-6 6-3 5-7 6-4 7-5.
Del Potro, who won last week's Sydney International warm-up tournament, sent down 28 aces and had 18 fewer unforced errors than his Spanish opponent but his tally of 53 winners was 19 adrift of Bautista.
"It's tough when someone plays at a very high level for four hours, tough to beat the opponent," said Argentina's top-ranked player.
"I was close. But at every moment that I had a chance, he played an unbelievable shot."
In the men's doubles, Briton Jamie Murray and Australian John Peers progressed to the second round - although Murray was later treated for heatstroke.