Elsewhere, three-time former champion Novak Djokovic faced Frenchman Valentin Royer on Court Philippe Chatrier, which has a roof, and was on court for three hours and 44 minutes.
The 39-year-old Serb lost a tight third set on a tie-break but regrouped to win 6-3 6-2 6-7 (7-9) 6-3.
In his post-match press conference, Djokovic suggested scheduling matches at Grand Slams later in the evening could be “something to consider” as a potential alternative if extreme conditions are expected.
French Open organisers monitor the temperature through two wet bulb sensors – one on Chatrier and another on Court 14.
If the threshold is reached, a 10-minute break may be introduced after the second set of women’s matches and the third set of men’s matches.
If temperatures continue to rise, matches can be suspended until the heat drops.
No French Open match has ever been halted because of extreme heat.
Women’s 15th seed Marta Kostyuk said the conditions so far this week are not quite as bad as those she experienced when playing at the same venue for the Olympics in 2024, but added: “It’s still hot and it’s very dry. I always felt like I need to drink, I want to drink more and more. It was tough.”
On Monday, former finalist Casper Ruud said he felt he was “walking around like a zombie” and feared he had heat stroke after struggling with cramping in 33C temperatures.
One player who escaped the worst of the conditions on Wednesday was men’s second seed Alexander Zverev, who played in the night session when temperatures had dropped to about 18C.
A runner-up at Roland Garros in 2024, Zverev continued his bid for a maiden Grand Slam with a dominant display to beat Czech player Tomas Machac 6-4 6-2 6-2 in one hour and 48 minutes.
