The Extreme Heat Policy has come into effect on day four at Australian Open 2014.
Temperatures in Melbourne have soared above 40 degrees Celsius on Thursday, bringing the rule into effect.
The rule means that current matches on court will be suspended at the end of the current set.
The roof at Rod Laver Arena and Hisense Arena will be closed at the end of the set so play can resume on those courts. Once closed it remains shut until the end of the match.
For outside courts, play will be suspended at the end of the set until further notice. No matches will be called to outside courts while the Extreme Heat Policy is in place.
Update 3.00pm local time: Play will not resume on outside courts until at least 5pm local time. Matches at Rod Laver Arena and Hisense Arena will continue with a closed roof.
Update 5.00pm local time: Play is scheduled to resume on outside courts at 6pm local time.
The full extreme heat policy can be viewed here.