As the temperature edged past 30 degrees Celsius (86 Fahrenheit) on Monday, the line at the frozen slushie stand was more than 30 deep and crowds were jostling to get in front of the giant fans blowing cool mist into the air.
On court, a couple players held ice bags against their faces and necks during change-overs. Sweaty shirts were stripped off with increasing regularity.
This is just the prelude, too. The forecast for the rest of the week is far more brutal, with highs expected to top 40 Celsius on Tuesday (104 Fahrenheit) and every day through Friday.
The concern for tournament officials is how the stifling heat will affect the players, staff and fans and whether they'll be forced to invoke the extreme heat policy and suspend play on the outer courts and close the roof and turn on the air-conditioning at the two courts with retractable roofs, Rod Laver Arena and Hisense Arena.
Tournament referee Wayne McKewen said the heat policy is based on the wet bulb globe temperature (WBGT), which takes into account a variety of factors including the air temperature, humidity and wind speed.
The temperatures could reach 42 degrees Celsius (107 F), for instance, and the players could still be on the courts if the humidity is low enough. It's up to McKewen's discretion when to enact the extreme heat policy.
"I don't like to have a set guideline because if we know it's going to be fluctuating ... then we will make a decision based on that. If we know it's going to spike, we can bring it in sooner rather than later for the players," he said.
Other precautions will be taken as the WBGT rises, short of calling play, McKewen said. At a reading of 26, for instance, ice vests are provided to all players on the courts. At 28, there is a 10-minute break after the second set for players in the junior singles event and a 15-minute break for the wheelchair events.
At a reading of 30.1, there's a mandatory 10-minute break in women's singles if the players split the first two sets.
McKewen said he also receives input from trainers after a player has had a particularly greuling match in the heat and give that player a later starting time in their subsequent match.
Despite the concerns of organizers, Tim Wood, the tournament's chief medical officer, said tennis players have a relatively low risk of experiencing medical problems in the extreme heat.
"We look into the health and well-being of players but we know over the years in different parts of the country and world, they play under these conditions," he said. "A lot of people get hot and look distressed and hot and bothered. The actual risk to the health is relatively small compared with other sports."
By and large, the players said they were prepared for the heat.
"It's never been a problem for me," said eighth-seeded Stanislas Wawrinka, who probably didn't experience many heat waves growing up in Switzerland. "It's the same for every player so you need to be ready."
"For sure I'm not going to practice three hours during the afternoon, but I will be ready for my next match."
Defending champion Novak Djokovic said before the tournament began that he's come to expect scorching conditions Down Under. After struggling at times in the Australian heat when he was younger, he has focused on improving his training in recent years so he can be fit enough to play five sets in extreme conditions.
"I mean, the experience of playing many times in the Australian summer over the years definitely helps for the preparations," he said. "But I don't change anything in particular in my approach. Everything is more or less the same."