Officials have played down health risks, saying the majority of matches were completed without calls for medical attention.
"Of course there were a few players who experienced heat-related illness or discomfort, but none required significant medical intervention after they had completed their match," Tim Wood, the tournament's chief medical officer, said in a statement.
A ball girl was treated for heat stress during a morning match, and the tournament shortened rotations for the ball kids to 45-minute shifts.
Players used metaphors and anecdotes to describe how hot it was.
"I put the (water) bottle down on the court and it started melting a little bit underneath -- the plastic. So you know it was warm," former No. 1-ranked Caroline Wozniacki said. "It felt like I was playing in a sauna."
Wozniacki was luckier than most. She had a straight sets win in the morning when it was 38C (100F).
Sometimes a hot breeze stirred the air, making things worse, said No. 13-seeded John Isner, who retired from his first-round match with a right ankle injury.
"It was like an oven -- when I open the oven and the potatoes are done. That's what it's like," Isner said.
Two-time defending champion Victoria Azarenka agreed.
"It felt pretty hot, like you're dancing in a frying pan or something like that," she said after advancing to the second round.
Always cool under pressure, Roger Federer avoided touching the hot ground at changeovers by sitting on his bench with his feet up on a towel. The 17-time Grand Slam winner advanced to the second round, saying for him the heat was "just a mental thing."
No. 4 Andy Murray struck a more sober tone.
"As much as it's easy to say the conditions are safe," Murray said, "It only takes one bad thing to happen."
"It looks terrible for the whole sport when people are collapsing, ball kids are collapsing, people in the stands are collapsing," the Wimbledon champion said. "That's obviously not great.
