It got so hot and humid at the US Open on Tuesday that the folks in charge adopted a new policy for the rest of this year’s tournament: They will partially shut the Arthur Ashe Stadium roof in extreme conditions to offer some extra shade.

The temperature climbed above 32 degrees Celsius and the humidity topped 50 per cent on Tuesday.

The change to the roof policy was made during Coco Gauff’s 6-0, 6-2 victory over Jelena Ostapenko, when the conditions crossed a threshold for protecting players in the heat.

The new policy is “in the best interest of fans and players,” tournament referee Jake Garner said. The forecast calls for even hotter temperatures in the coming days.

The Arthur Ashe Stadium roof was partly closed before Novak Djokovic’s 6-1, 6-4, 6-4 win against Taylor Fritz. It still was so muggy in there that Djokovic poured water over his head during one changeover; Fritz removed his shirt and placed a rolled-up towel filled with ice around his neck during another.

“I’m drenched in sweat,” Djokovic told the crowd in an on-court interview. Fritz thought having less of an opening above the stadium increased how humid it seemed. “It was definitely hot... I’d say it’s more the humidity than anything,” the ninth-seeded American said. “I don’t feel like I’m ever bothered too much by the heat. I feel like (when) it’s just really humid ... it just drains you.”

The roof on Louis Armstrong Stadium was pulled shut some of the way after the first set of a women’s doubles quarterfinal with Magda Linette and Bernarda Pera against Jennifer Brady and Luisa Stefani.