New York has been sweltering in a heatwave this week, with high humidity and temperatures at Flushing Meadows on Wednesday hitting 35 degrees Celsius (95 Fahrenheit)

Novak Djokovic suffered his first loss of the season in Friday's semi-final defeat to Daniil Medvedev at the Dubai Tennis Championships but he was pleased with his fitness levels during the tournament, having returned from a hamstring injury.