US Open: Players struggle in stifling heat as Djokovic's opponent retires hurt

With around 55 million people placed under heat alerts, players and fans at the US Open on Wednesday struggled to keep cool as temperatures rocketed.

In the middle of the afternoon at Flushing Meadows, the searing heat reached 35 degrees Celsius (95 Fahrenheit).

"I'm sweating crazy. What was it, 95 degrees outside? Today was crazy," said American star Frances Tiafoe whose opponent Alexander Shevchenko retired in the third set of their second round clash.

Tiafoe discarded five shirts in a sweaty pile next to his chair on the Arthur Ashe Stadium.

Steamy conditions tested players' resolve but defending champions Novak Djokovic and Coco Gauff both advanced to the third round, while Aryna Sabalenka marked her win by taking photographs with a mini version of herself.

Sweat-soaked 24-times Grand Slam champion Djokovic looked far from comfortable under the lights at Arthur Ashe Stadium and had to battle from 2-4 in the second set before seeing off fellow Serb Laslo Djere, who retired injured at 6-4 6-4 2-0.

"It's not what we want. It's not what the crowd wants, to see a walkover," Djokovic said.

"But he obviously had an injury that took him out of the tour for some time and he is struggling to come back physically to this level. He's such a good player, especially in these conditions. It should have been his second set.”

German fourth seed Alexander Zverev wasted little time in blazing conditions earlier in the day as he dispatched Frenchman Alexandre Muller 6-4 7-6(5) 6-1 on Louis Armstrong Stadium.

"I'm happy to be through in three sets because I think the weather and conditions were obviously very difficult today. Very hot, very humid," Zverev said.

"The less time I spend on the court, the better it is."

Russia's Andrey Rublev, American teenager Iva Jovic and Victoria Azarenka all summoned doctors courtside.

Rublev, who needed five sets and more than four hours to defeat Arthur Rinderknech, told medical staff he had drank so much water that he felt he had "a baby" in his stomach.

Ukraine's Marta Kostyuk defeated Britain's Harriet Dart and spent the changeovers with an ice towel around her neck, an ice pack on her head and two wet towels under her legs.

Kostyuk even sent ice towels to her coaching staff watching from the sidelines.

During the day, the roofs on the two man show courts -- Arthur Ashe and Louis Armstrong stadiums were partly closed to provide desperately needed shade.

Officials also invoked the extreme heat rule which allows players to take a 10-minute break to recharge.

For men, the rule came into effect between the third and fourth sets; for women, between the second and third.

That was of little comfort to Tomas Etcheverry who vomited on court during his five-set, four-hour win against Argentine compatriot Francisco Cerundolo.

"The temperature was 38 degrees and to that we have to add another four degrees inside the court," said Etcheverry.

"You had to hydrate well, try to take as many salts and hydrates as possible and I overdid it, that's why I ended up vomiting.

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