Victoria Azarenka began her bid for a third consecutive Australian Open title with a 7-6 (2), 6-2 win over Johanna Larsson on Tuesday as the start of a predicted heat wave arrived at Melbourne Park.
Conscious of the time and the temperature, former No. 1-ranked Caroline Wozniacki and No. 11 Simona Halep raced to straight-set wins in their first-round matches on the other show courts.
Second-ranked Azarenka had a tougher time on Rod Laver Arena against Larsson, who twice had chances to serve for the first set but lost it in a tiebreaker.
"Yeah it was a tough set first. The match was going to be tricky ... the weather was not helping," Azarenka said. "I had to play a little bit and find my rhythm."
Both players had trouble holding serve, with a combined six service breaks in 66 minutes leading into the tiebreaker. No. 91-ranked Larsson was taking big cuts with her ground strokes and forcing Azarenka to defend. But the two-time defending champion started getting on top in the second set and didn't drop serve again.
Both players draped bags of ice over their necks and shoulders and sat under covered seats in the changeovers. They retreated into the shade at the back of the courts between points.
Temperatures hit 40 Celsius (104 Fahrenheit) early on the second afternoon of the tournament and was expected to rise. A hot, gusty breeze swirled across the venue. Spectators on outside courts covered their heads and shoulders with damp towels to cool off.
No. 13 John Isner, the only seeded American man in the draw, retired after losing the first two sets 6-2, 7-6 (6) against Martin Klizan. He called for the trainer after the tiebreaker, tapped his racket on the ground three times while deliberating whether to go back out, and only played on for a few minutes in the third set. Tournament officials said he retired with a foot injury - Isner won the title last weekend at Auckland, where he was playing with an injured right ankle.
It was the second retirement in as many matches on Court 6. No. 25 Alize Cornet only had to win one game before Polona Hercog of Slovenia retired with an undisclosed injury. Philipp Kohlschreiber of Germany didn't make it onto court, withdrawing before his first-round match due to a strained left hamstring.
The No. 21-seeded Kohlschreiber was replaced in the draw by Frenchman Stephane Robert, who beat Slovenia's Aljaz Bedene 7-6 (3), 6-3, 6-0.
With the hot conditions forecast to continue at least until Friday, the higher-ranked players were desperate to progress quickly.
Wozniacki had a 6-0, 6-2 win over Lourdes Dominguez Lino in her first Grand Slam match since her New Year's Eve engagement to golfer Rory McIlroy, doing everything she could to keep cool.
"Every time in the changeovers, ice bags, ice towels, everything; and then in the second set I could feel they were starting to heat up even more," Wozniacki said.
"I put the bottle down on the court and it started melting a little bit underneath, the plastic, so you knew it was warm."
Halep had a 6-0, 6-1 win over Polish qualifier Katarzyna Piter, while American Christina McHale advanced 7-5, 6-4 over Taiwan's Chang Yung-jan and No. 16 Carla Suarez Navarro of Spain beat Vania King of the United States 6-3, 6-2.
The tournament started in milder conditions Monday, with top-ranked Serena Williams capped off the first day with a 6-2, 6-1 win over Ashleigh Barty to extend her winning streak to 23 matches.
Three-time defending champion Novak Djokovic improved his winning streak at Melbourne Park to 22 matches with a routine win over Lukas Lacko of Slovakia.
The loaded top half of the men's draw starts later Tuesday, with No. 1 Rafael Nadal, 17-time Grand Slam winner Roger Federer, Wimbledon champion Andy Murray and No. 5-ranked Juan Martin del Potro all in action.