Australian Open organisers were forced to implement their extreme heat protocols, as Melbourne Park dealt with scorching weather conditions.

Play was suspended on the outside courts shortly after 2:30pm AEDT, while the roofs were closed on the arena venues so matches could continue indoors.

Organisers made the decision to suspend play when its heat stress scale reached the maximum reading of five.

The temperature hit 38 degrees Celsius around 3pm AEDT, two below the forecast high.

Matches on the outside courts will not resume before 6:30pm AEDT.

A man cools down in front of a water mister at Melbourne Park.

A spectator cools down in front of the fans at Melbourne Park. (Getty Images:  James D Morgan)

Play began early on day seven, with the first roster of matches commencing at 10:30am AEDT.

Among those to complete their third-round matches was women’s sixth seed Jessica Pegula, who defeated Oksana Selekhmeteva 6-3, 6-2.

Australian Open: day seven blog

Play is suspended and roofs closed at Melbourne Park as sweltering temperatures forced players off court.

Pegula completed her victory in an hour and six minutes on Margaret Court Arena, avoiding the hotter conditions that descended on Melbourne Park in the afternoon.

“It started to get a little hot,” Pegula told her post-match media conference.

“I just tried to use the ice towels as much as I could, just pre-cooling a lot.

“Not necessarily [because] it felt that hot at the moment, but if it did start to creep up or if something happened and we go into a third (set), I definitely think it could kind of zap you pretty quick.

“The fact that we haven’t been playing that much in the hot temperatures is what gets people, I think. You have no kind of tolerance to it.”

Madison Keys drinks from a water bottle at the Australian Open.

Madison Keys was among the first players who took to the courts. (AP: Asanka Brendon Ratnayake)

Defending champion Madison Keys, who faces fellow American Pegula in the fourth round, also played in the morning.

Ninth-seeded Keys defeated Karolína Plíšková 6-3, 6-3 on Rod Laver Arena, although she was not troubled by the heat.

“I didn’t really notice it that much, to be honest,” she said.

“Coming off the court, I was actually kind of surprised by how hot it was actually reading.

“It didn’t feel that bad to me out there, but it obviously helps finishing as early as we did.”

Saturday will not be the only day in which the Australian Open will have to deal with extreme heat.

Tuesday’s long-range forecast is above 40C.