Australian Open practice was temporarily suspended on Tuesday and qualifying delayed by an hour because of poor air quality in Melbourne caused by ongoing bushfires.
Organisers said the conditions were expected to improve and would be “monitored constantly”.
An estimated 10 million hectares (100,000 sq km) of land has burned since 1 July amid record-breaking temperatures and months of drought.
At least 28 people have died.
Qualifying was scheduled to begin at 11am local time (00:00 GMT) with British players Liam Broady, Naiktha Bains, Harriet Dart, Jay Clarke and Samantha Murray scheduled on court.
However, in the hour before the scheduled start time the air quality around Melbourne Park was registering at 229 on the Air Quality Index, which is considered “very unhealthy”.
“Further decisions will be made based on onsite data, and in close consultation with our medical team, the Bureau of Meteorology and scientists from EPA Victoria,” organisers said in a statement on Twitter.
“As always the health and safety of our players, our staff and our fans is our priority.”
The tournament starts on 20 January.
Last week organisers said they did not expect any delays, with tournament director Craig Tiley saying the forecast was good.
On Monday, the The International Tennis Federation, Wimbledon, and the US and French Opens donated $400,000 (£308,000) to the Australian Bushfire relief efforts.
Several players have already pledged personal donations towards relief efforts as part of the #Aces4BushRelief campaign, while the ATP is donating £383,000.
Serena Williams donated her earnings after winning the Auckland Classic, and she along with Rafael Nadal, Roger Federer and local favourite Nick Kyrgios will take part in the Rally4Relief exhibition in Melbourne on Wednesday to raise money before the Australian Open.
Former Australia cricketer Shane Warne raised over £500,000 by auctioning off his ‘baggy green’ cap, and he and former Australia captain Ricky Ponting will captain opposing sides in a special Twenty20 game on 8 February.
Article courtesy of BBC Sport