Novak Djokovic has said that the conditions affected him during his straight-sets victory over Andreas Seppi.
The world number three won 6-3 7-5 7-5 but failed to play his best tennis due to the 27 degree heat at Flushing Meadows.
"[The key was to] hang in there, try to create my own pace. It's not easy to maintain control of the rallies because he stays close to the line and plays very quick," Djokovic told ESPN.
"I knew he was going to be aggressive and it was a tough three sets.
"It's not easy. It's very humid so I'm glad to get through this one."
The Serbian will play against either David Goffin or Roberto Bautista Agut in the fourth round.
