Stosur, who had warned the officials that conditions were becoming dangerous for players, lost to world No.2 Caroline Wozniacki 6-3 6-2.

The mercury had hit 35 degrees Celsius before 2 pm with the heat affecting the players severely as there had been four retirements in the men's event by mid-afternoon.

“You do have to be careful. There were a couple of incidents yesterday as well and I think you’ve got to be sensible,” Stosur told AAP.

“It was just bloody hot. I was drenched straight away … I mean, I felt fine but it was tough out there,” she said.

The USTA implemented the extreme heat policy which offered players a 10-minute break before deciding third sets in the women's draw with the men having a similar rule.

Stosur, who was born and raised in Brisbane said the weather was like being in tropical Queensland but much more uncomfortable than her experience at the Australian Open.

However, she reiterated that the conditions had no impact on her performance.

The 34-year-old finished with eight double-faults and 34 unforced errors.

“I thought I played a pretty decent match. I’m actually proud of myself with what I was able to do out there,” she said.

“Obviously there were things I wasn’t so happy with but, overall, I was obviously playing a quality opponent and gave it everything I had.

“The one thing that probably did let me down was my second serve," Stosur said.

Australia does have a third joining Daria Garilova and Ash Barty in the second as Anja Tomljanović cruised to a 6-4 6-1 victory over fellow Australian Lizette Cabrera.