No. 25 Alize Cornet of France sobbed on court after her draining 6-3, 4-6, 6-4 victory over Italian Camila Giorgi, which ended after 2½ hours.
"I went really further than my limits," she said in her on-court interview. "It was really hot, that's why I'm so emotional.
"Doing something physical in this heat it's just unbelievable -- Even you guys (in the crowd) sitting in the sun, it must be terrible."
The seats with no shade on the outer courts were virtually empty, with spectators congregating instead under trees on the sides of courts or in the upper reaches of stands where temporary covers provided a little relief.
New Zealander Helen Naylor escaped the sun after watching fellow Kiwi Marina Erakovic play part of a set against Kazakhstan's Zarina Diyas on Court 13.
"Even the seats are really hot so I've got an overheated bum, which is not very comfortable," she said. "God knows how (the players) are running around out there."