Organisers urged everyone attending the 50th edition of the tournament in Flushing Meadows Park to drink plenty of water and use sunscreen to protect themselves. Yet they said they would not close the roof on either of the two stadiums due to the heat.

The new 14,000-seat Louis Armstrong Stadium does not have an air conditioning system but relies on a first-of-its-kind natural ventilation system, which will be put to the test as temperatures are expected to soar well above 90 Fahrenheit (32C).

The roofs on Arthur Ashe stadium and Louis Armstrong stadium will likely be shut on Friday, however, as rain is forecast and expected to bring relief from the heat. It could also throw a wrench in the tournament’s busy schedule.

As for the players who have to cope with the sweltering conditions, it is all part of the brutal test that is the fourth and final Grand Slam of the year.

“It’s one of the reasons the US Open is the toughest test in tennis,” USTA spokesman Chris Widmaier told Reuters on Tuesday.

Several players requested medical attention due to the heat during their matches on Monday while some on the women’s side opted to take advantage of a 10-minute heat break between the second and third sets of their matches.