The temperature at the USTA Billie Jean King National Tennis Center in Corona Park hit 32C with the humidity around 60 per cent.
On the WTA tour, players are able to take a break between the second and third sets if the temperature hits a certain mark.
And No 10 seed Jelena Ostapenko and Andrea Petkovic split the first two sets and left the court on Louis Armstrong Stadium for 10 minutes.
But the USTA have confirmed male players will have the option to take a break if either one requests it.
The USTA said: “Upon the recommendation of the US Open medical team, the Extreme Heat Policy will be implemented immediately for Men’s matches.
“The men will be offered a 10-minute break between the third and fourth set.”
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