Soaring temperatures have forced matches at the Australian Open to be suspended after the tournament referee applied the extreme heat policy at Melbourne Park.
Temperatures hit 42 degrees on day four of the grand slam, with tournament referee Wayne McEwen deeming conditions unsafe for players.
The announcement came at 1.52pm, with all matches in play on the outside courts now suspended after the set in progress came to an end.Play on outside courts won't resume any earlier than 5pm.
However on Rod Laver Arena and Hisense Arena, play continues with the roof to be closed at the conclusion of the set - barring any objections from the match referee.
At the time of the suspension, No.3 seed Maria Sharapova and Italian Karin Knapp were locked in a tense final-set decider having been on court for more than three hours. They played for a further 50 minutes after the announcement before Sharapova eventually triumphed 10-8 in the third set.
The extreme heat policy is applied when the Wet Bulb Globe Temperature exceeds a predetermined threshold, allowing the tournament referee to suspend play at his discretion.
Given the extreme heat in Melbourne, women in the singles draw were already allowed a 10-minute break between the second and third sets and ice vests are provided on all courts.
Matches interrupted because of the extreme heat policy include Jo-Wilfried Tsonga's match against Thomaz Bellucci and Andreas Seppi versus Donald Young. The Tsonga-Bellucci match restarted when the roof was closed on Hisense Arena.
Earlier, tournament referee Wayne McKewen said while conditions so far this week had not warranted the extreme heat policy to be implemented, “today may be a different story based on forecasts”.
Speaking to Melbourne radio station 3AW, Mr McKewen said weather conditions were being “continually re-assessed” and that he was in regular contact with the tournament's chief medical doctor and the Bureau of Meteorology, which has set up a temporary base at Melbourne Park.
The forecast top for Melbourne on Thursday is 44 degrees. Friday is expected to reach 42 ahead of a gusty change.
“We've got staff in the tournament control who are continually monitoring the weather conditions,” he said, adding that ambient air temperature, humidity and wind variation were all considered.
Mr McKewen said he was confident the regulations protected players' health and safety, despite removing the phrase “predetermined threshold” from the tournament's heat policy earlier in the week.
“I've got guidlines which I follow,” he said. “We don't want to have a hard mark as to, ok if it hits this we stop play.
"Because we all know in Melbourne temperatures can fluctuate very quickly, and if we know it's going to cool down in the next half an hour or so we'll push through that period and then continue on into the cooler period. But if I know the temperatures will spike I would rather bring everyone in earlier rather than later.”
“We want to have that little bit of flexibility for the players.”
Nine players retired during the first round, some due to heat.