With the mercury hitting 35 Celsius (95 Fahrenheit) before play even started, players and fans were feeling the heat at Melbourne Park where 64 matches were on the agenda.
Defending women's champion Victoria Azarenka and Caroline Wozniacki, both on court at 11:00 am for their round one matches, grimaced and sweated in the bright sun and draped themselves in ice packs during changeovers. (Read: Azarenka stutters to a win)
Swiss great Roger Federer will follow Azarenka onto the centre court when he faces Australia's James Duckworth in what are likely to be the day's hottest temperatures.
"Geez, it feels hot out there," said Wozniacki after her win over Lourdes Dominguez Lino. "It feels like I was sweating in a sauna or something.
"It's really tough... I was just trying to take the ice towel as much as I could and try not to think about the heat, like I'm in Alaska or something."
Temperatures are forecast to hit 43 Celsius Tuesday, shy of Melbourne's January record of 45.6 Celsius during the notorious Black Friday bushfires of 1936.
High temperatures are expected to remain for most of the week, in similar conditions to the 2009 Black Saturday bushfire disaster which killed 173 and injured hundreds more.
Emergency officials announced a blanket fire ban across Victoria and warned of extreme temperatures in parts of the state.
At Melbourne Park, the tennis venue near the centre of the state capital, unshaded seating areas lay largely empty as fans stayed out of the sun.
Volunteers handed out sunscreen as spectators entered the venue wearing sombreros, umbrella hats and sunglasses, and a young girl frolicked in a fountain to stay cool.
The Australian Open is no stranger to extreme heat with many incidences in the past, but few occasions when play has been suspended.
In 2009, the hottest Australian Open on record with an average daily temperature of 34.7 Celsius, defending champion Novak Djokovic pulled out of his quarter-final with Andy Roddick, citing heat exhaustion.
By 12:30 pm (0130 GMT), the official temperature was given as 38.2 Celsius.
It's the Australian Oven as temperatures soar
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