The extreme heat policy has been put into effect for the third successive day at the US Open.
Although temperatures were forecast to be a little lower than the previous two days, they were still expected to be well over 30C Celsius with considerable humidity until possible thunderstorms later in the day.
A severe weather alert for New York was issued until 8pm local time.
The policy means a 10-minute break is permitted between the second and third sets of women's matches and the third and fourth sets of men's matches, while medical time-outs for heat-related illness are also allowed.
