Australian Open - 'Very dangerous' heat, then lightning wreaks havoc

Play at the Australian Open was called to a halt for more than four hours on day four with temperatures at Melbourne Park hitting 43.3 degrees Celsius.

Later in the day, at just before 0900 GMT, lightning and thunder then hit Melbourne Park as the blazing hot weather finally broke, with play suspended once again on the outside courts as weather played havoc with the schedule of play.

Organisers, who had been slammed for forcing players to play on in searing temperatures on Tuesday and Wednesday, enacted the third stage of their "Extreme Heat Policy" for the first time at about 1.50pm local time (0250 GMT).

Play continued on the Rod Laver Arena and Hisense Arena, however, after the retractable roofs over the main show courts were closed.

With players having to finish the ongoing set before play ceased or the roofs were closed, however, Maria Sharapova's match on Rod Laver Arena continued in the full glare of the sun for 50 minutes after the policy was enacted.

The third seed eventually finished off Italian Karin Knapp 6-3 4-6 10-8 to reach the third round.

"I remember being really close to passing out but I'm feeling much better now," Sharapova said in a courtside interview. "I think I'm just getting numb to it."

With forecast highs of 44 degrees Celsius, another day of suffocating heat at the year's first grand slam was guaranteed to keep the debate on whether play should continue rumbling on.

American Varvara Lepchenko clearly struggled in the heat in the first match on court eight, which she lost 4-6 6-0 6-1 to Romanian Simona Halep.

"I think they definitely should have not started the matches at first place," Lepchenko said.

"I think they should have started the matches after the temperature cooled down a little bit because this is just too much.

"Obviously it is very dangerous if someone has conditions with their heart or anything like that or just being in this temperature it's almost like going to (the) sauna."

On Tuesday, when temperatures peaked at 42.2 degrees, Canadian Frank Dancevic passed out during his first round match and accused organisers of forcing players to play in "inhumane" conditions.

Ivan Dodig became the 10th player to retire in the first three days of the tournament on Wednesday and said he feared for his life after being rendered immobile by the heat on the exposed outer courts.

Under a change to the rules for this year, the decision on whether to stop matches at the tournament is now at the discretion of tournament referee Wayne McKewen.

Rather than use the raw Celsius readings to assess the heat, organisers prefer to use the Wet Bulb Global Temperature composite, which also gauges humidity and wind to identify the perceived conditions.

McKewen said that the threshold was not reached on Tuesday and Wednesday with world number seven Tomas Berdych suggesting that perhaps it had been set too high.

The hot weather is forecast to continue through Friday before a dramatic drop in temperatures at the weekend.