Victoria Azarenka began her bid for a third consecutive Australian Open title with a 7-6 (2), 6-2 win over Johanna Larsson as the predicted heat wave arrived at Melbourne Park.
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 in the first set. The two-time defending champion started getting on top in the second and didn't drop serve once. Both players draped bags of ice over their necks and shoulders and sat under cover in the changeovers, and went to the back of the courts seeking shade between points.
Temperatures topped 38 Celsius (100 Fahrenheit) early on the second day of the tournament and continued to rise. A hot, gusty breeze swirled across the venue.
With the hot conditions forecast to last at least until Friday, the higher-ranked players were desperate to progress quickly.
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.
The tournament started in milder conditions on Monday, and top-ranked Serena Williams capped off the night session with a 6-2, 6-1 win over 17-year-old Australian wild-card entry Ashleigh Barty to extend her winning streak to 23 matches.
Not all the highly-ranked players made it through on the opening day on the women's side, with sixth-seeded Petra Kvitova, the 2011 Wimbledon champion, losing to Luksika Kumkhum of Thailand, following seventh-seeded Sara Errani and No. 12 Roberta Vinci out of the tournament.
Novak Djokovic improved his winning streak at Melbourne Park to 22 matches as he commenced his bid for a fourth consecutive Australian Open title with a 6-3, 7-6 (2), 6-1 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.