Defending champion Novak Djokovic advaced to third round by beating Argentine Leonardo Mayer 6-0 6-4 6-4 as the mercury soared.
He was joined in the third round by Tomas Berdych and World No.3 David Ferrer, who dropped a set, beating Adrian Mannarino 7-6 5-7 6-0 6-3.
Berdych said conditions on Hisense Arena were as hot as he had encountered in a career that has stretched more than a decade.
The Czech moved into the third round with a straight sets win over Frenchman Kenny De Schepper 6-4 6-1 6-3, The Herald Sun reports.
Russia's Mikhail Youzhny became the first men's seed to lose.
He went down 6-4 3-6 6-3 3-6 6-3 to Germany's Florian Mayer as the temperature again hit 40C.
