How 'lucky' Sinner became biggest winner in near 40C Melbourne heat

Jannik Sinner's ambitions of winning a third straight Australian Open title looked close to being over as the Melbourne heat crept towards 40C.

In the end, the rising temperatures helped the cramping Italian come through a testing third-round match - because the Grand Slam tournament's heat rule was invoked.

Only coming off court and having the roof pulled over saved Sinner from a shock defeat by American world number 85 Eliot Spizzirri.

"I got lucky with the heat rule," conceded Sinner, who came through to win 4-6 6-3 6-4 6-4.

Sinner was undoubtedly the biggest winner on a sweltering day where play was suspended and almost 100,000 fans were warned to take care in the heat.

Matches on the show courts are being played in cooler conditions under the roof, but play on the outside courts did not resume until 19:30 local time because of the heat.

Mist tunnels, water machines and sun umbrellas helped cool down spectators.

Ball kids placed their hands on their feet - instead of the court - to avoid burning their palms when crouching at the net post.

American player Jessica Pegula says the stars are "used to" the searing heat, but Saturday's conditions were a reminder of how brutal it can be at Melbourne Park.

Play is stopped at the Australian Open when the heat stress scale hits its maximum of five.

The scale measures four factors: radiant heat (or the strength of the sun), air temperature in the shade, relative humidity and wind speed.

When Sinner and Spizzirri took to court at about 12:30 for the second match on Rod Laver Arena, chair umpire Fergus Murphy reminded the players about the protocols which could be enforced.

With the match level at one set all, Sinner could barely walk at the start of the third set and fell a break down at 3-1.

Then came a huge slice of fortune in a moment of sporting theatre.

Seconds after the fourth game, with Sinner looking finished, the heat stress scale hit five - meaning the top seed was able to go off court.

It was pivotal in the momentum of the match.

There is no question the rule benefitted the red-headed Sinner, who also struggled in the Melbourne heat against Holger Rune last year and immediately limped to the locker room.

Spizzirri looked bemused as he shook his head. But the rules were implemented correctly.

Matches on the show courts stop at the end of an even game so the roof can be closed and allow the air circulation system to cool the arena.

Sinner broke back immediately after an eight-minute delay and, while still moving tentatively, took Spizzirri's serve again for 5-4 and secured the third set.

Sinner now looked much more comfortable in his movement, even though he often stayed stood at the change of ends, and his ball-striking became too much for Spizzirri to handle.

The temperature dropped to about 26C during the fourth set as Sinner secured a dramatic victory and gave a relieved puff of his cheeks.

Tournament organisers brought Saturday's play forward by 30 minutes to 10:30 local time in anticipation of the high temperatures.

It always looked likely the action would be suspended in the afternoon, given the Australian Bureau of Meteorology had issued a severe heatwave warning.

British junior Hollie Smart was among the early starters and had to retire from her first-round match after also suffering cramp.

Defending women's champion Madison Keys and her fellow American Pegula were grateful their respective matches were scheduled in the morning.

"I'm super happy to be able to get out there before the heat got extreme. Just get in and get out early," said Keys, who won 6-3 6-3 against Czech Karolina Pliskova.

Pegula, who won 6-3 6-2 against Russia's Oksana Selekhmeteva, said the conditions were "different but not crazy".

"I think we're all used to it. I think I would much rather have played first and hopefully won efficiently enough to get out of that heat as quick as possible," she added.

Ball boys and girls worked 45-minute rotations instead of the usual one hour, with an increased one-and-a-half-hour break between shifts.

Fans were reminded to stay vigilant and take precautions.

The Australian Open said facilities throughout the site would help people cool down, including:

Temperatures are also predicted to top 40C on Tuesday, when the singles quarter-finals are scheduled to begin.

"The weather being crazy [means] a lot of adjustment on the strings and your approach to the match," said women's world number one Aryna Sabalenka, who plays Canadian teenager Victoria Mboko in the fourth round on Sunday.

"It's going like a rollercoaster. We'll see who adjusts better in the next days."