Suncream, hats and icepacks were the order of the day and spectators cooled off under misting fans as the temperature hit the 40 degrees Celsius mark in late afternoon.
Third seed Williams did her best to keep her time on court to a minimum as she swept aside Garbine Muguruza 6-2 6-0.
Victoria Azarenka may be the defending champion and world number one but Williams is odds-on favourite to capture a 16th Grand Slam title and a sixth in Australia next week.
The Belarussian proceeded easily enough with a 6-1 6-0 thrashing of Eleni Daniilidou but any hopes she had that Williams, against whom she has a 1-11 record, might be hampered by the ankle she injured on Tuesday were quickly dashed.
Williams split her lip with her own racket during the first set against her lowly-ranked opponent, but was barely troubled thereafter and set up a meeting with Japan's Ayumi Morita with her 10th ace of the match.
"I didn't feel anything today," the 31-year-old said of the ankle injury. "Obviously when you go out to play you're heavy on adrenaline and you're really pumped up.
"Usually I feel injuries after the match, but so far, so good. I felt much better than I ever dreamed of expecting to feel.
"I'm on the up and up. It can only get better from here."
Kimiko Date-Krumm, the women's world number 100, continued her fairytale run some 23 years after making her Australian Open debut with a victory over a player 17 years her junior.
The 42-year-old Japanese is fast becoming a cult hero at Melbourne Park and emerged a 6-2 7-5 winner over Shahar Peer of Israel after 92 minutes of exertion on court six.
"It's not easy, not easy," she said. "I need a new body."
Former world number one Caroline Wozniacki was also feeling her age after her encounter with Croatian teenager Donna Vekic, which she won 6-1 6-4.
"I've been out here for a few years now and I feel like a veteran. Particularly when I'm playing against a 16-year-old," she said.
"I'm seriously starting to feel old and I'm 22! I got asked a few months ago if I was going to retire."
Lesia Tsurenko, who beat Daria Gavrilova of Russia 7-5 6-3, is her next opponent.
Matches involving the top women have been particularly lop-sided and the first four seeds have yet to drop a set between them.
"I think I honestly can only speak for myself, but it seems like everybody is in great form, and it's going to be very interesting," said Azarenka.
A day after Maria Sharapova dished out a second successive 'double bagel' to an overmatched opponent, Azarenka was just as ruthless in dispatching Daniilidou 6-1 6-0 in 55 minutes on Rod Laver Arena.
Daniilidou won just 10 points in total in the first set, seven of which were achieved in the fifth and sixth games when she pressured Azarenka's serve and then held her own serve for the first time to ensure she did not suffer the dreaded 'double bagel' herself.
Azarenka was only pushed in one further game against the world number 94, when Daniilidou held three break points in the fourth game of the second set. Otherwise it was one-way traffic.
"I just try to win every game," Azarenka said in a statement that underlined her ruthless desire to retain the Daphne Akhurst Memorial Trophy.
"And of course when it's on my serve and even if it's on her serve, I just try to make every point the best as possible.
"If it's love-40 or whatever is the score, I'm going to fight for that point."
The Belarusian will now meet Jamie Hampton in the third round after the American beat Thailand's Luksika Kumkhum.
The outer courts were again the place to go for upsets as 21st seed Varvara Lepchenko was a 6-4 6-2 victim of Elena Vesnina on court two and 17th seeded Czech Lucie Safarova went down 7-5 7-5 to Bojana Jovanovski while Svetlana Kuznetsova blasted past 26th seed Su-Wei Hsieh 6-2 6-1.
Maria Kirilenko, Roberta Vinci, Yanina Wickmayer and Sloane Stephens were seeds who did make it through to the last 32.
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- Eleni Daniilidou
- Victoria Azarenka