Preparing to take the court Tuesday at the Australian Open, American Sloane Stephens kept checking the weather app on her phone as she fretted about the temperature.
The number kept climbing, and Stephens updated her coach, Paul Annacone.
"I'm like, 'My phone says 108.' He says, 'No, it can't be.' 'No, I'm pretty sure,'" Stephens recalled later.
Australia's summer heat wave has produced eye-popping, knee-buckling temperatures, and the mercury soared well beyond the century mark on Day 2 of the Grand Slam tournament in Melbourne. While the conditions were remarkable, so was the ability of the world's top players to endure them, undercutting their reputation as coddled complainers.
Touring pros must cope with the frustration of frequent rain delays at Wimbledon. Cool, damp weather often accompanies the French Open's marathon matches. Seasons change from summer to fall during the U.S. Open.
But the heat served up at the Australian Open poses perhaps the most challenging conditions on the Grand Slam circuit.
"It can become just a very mental thing, you know, and you just can't accept that it's hot," Roger Federer said. "Just deal with it, because it's the same for both. That's basically it."
Carolina Wozniacki of Denmark said the plastic on her water bottle began to melt when she set it down on the court during her match. But she said an ice bath helped her recover quickly afterward.
"I could go out and play another two sets now," Wozniacki said. "You know that it's going to be hot. It's Australia."
With more triple-digit temperatures in the forecast for Melbourne, here are five things to know while the heat is on:
GUIDELINES FOR HALTING PLAY: Matches can be stopped and the tournament's two retractable roofs closed at the discretion of tournament director Wayne McKewen. He makes his decision while monitoring the wet bulb globe temperature index, or WBGT, a calibration based on temperature, humidity, wind speed and sunshine. Extreme heat halted plays during several days of the 2006 tournament. The hottest Australian Open on record was in 2009, when the average temperature was 94.46 degrees (34.7 C).