Cloud cover and a gusting wind help keep temperatures just below the peak of 42.2 degrees Celsius they reached on Tuesday, when Canadian Frank Dancevic passed out and accused organisers forcing players to play in "inhumane" conditions.
Ivan Dodig became the 10th player to retire in the first three days of the tournament, though, when he was unable to complete his match against Bosnian Damir Dzumhur on one of the exposed outer courts.
"Today, 30 minutes after the match I could not walk," Croatian Dodig said. "There were 10 people around me. I was thinking I could maybe even die here.
"I think we deserve that somebody listens to the voice of the players."
Djokovic needed 107 minutes to take the second step on the path he hopes will take him to a fourth successive title by thrashing Argentine Leonardo Mayer 6-0 6-4 6-4 on Rod Laver Arena.
Williams, in the hunt for her sixth title, also hotfooted it into the third round with a one-sided 6-1 6-2 demolition of Vesna Dolonc before revealing her own particular visualisation technique for dealing with the heat.
"I just pretend I'm in Hawaii riding a wave, that's all I can do," she said after setting up an encounter with Daniela Hantuchova.
Djokovic was forced to retire from a match against Andy Roddick in another Melbourne heatwave five years ago but proved against Mayer that he was an altogether stronger player than in 2009.
"You don't want to spend too much time in the heat. You want to try to win as quick as possible," the second seed, who next faces Denis Istomin, told reporters.
"I prepared myself mentally for that. It's not just physically. Mentally you need to be tough enough to not give up and not think about what conditions can do to you."
World number one Williams was her usual mix of elegance in her dress and brutality in her play as she dismissed Dolonc in just over an hour on the same court.
Though no one could ever doubt the mental strength of a player who has won 17 grand slam titles, Williams did admit to a sleepless night worrying about the impact the heat might have on her bid to win her first title in four years in Melbourne.
"I kept waking up in the middle of the night last night, just paranoid," Williams told reporters.
"I just wanted to stay hydrated. The last thing I want to do is to cramp in this weather. It can happen so easy. I was just drinking a tremendous amount of water."
Williams has seen off at least a couple of generations of younger women looking to knock her off the top of the game and 16-year-old Belinda Bencic is tipped to be in the vanguard of the next wave.
The Swiss qualifier, coached by the mother of three-times Australian Open champion Martina Hingis, started poorly in her match against fourth seed Li Na but after losing the first seven games, rallied to force the second set into a tiebreak.
"She played exactly like Martina Hingis, I feel," Li said after her 6-0 7-6 (7-5) win.
Tomas Berdych, again sporting his distinctive blue and white striped shirt, was the first man into the third round when he hammered Frenchman Kenny De Schepper 6-4 6-1 6-3.
The seventh seeded Czech said conditions were the hottest he had played in and suggested that if the threshold for stopping matches had not been reached, it was probably set too high.
"I'm just trying to deal with that, trying to be ready, trying to survive it, and try to go as far as I can," he told reporters.
France's Richard Gasquet soon joined Berdych by beating Nikolay Davydenko 7-6 (7-3) 6-4 6-4 in match that featured a stunning point.
Davydenko looked to have clinched it with a no-look underarm shot from behind the baseline only for the ninth seed to hit an outrageous winner over his shoulder running back into the court away from the net.
Third seed David Ferrer continued his progress through a section of the draw further weakened by the by the 6-4 3-6 6-3 3-6 6-3 defeat of 14th seed Mikhail Youzhny at the hands of Florian Mayer on Wednesday.
Ferrer's unrelenting fighting spirit put him in good stead in his match over Frenchman Adrian Mannarino, who won the second set before wilting in the heat and going down 7-6 (7-2) 5-7 6-0 6-3.