Extreme heat predicted for Saturday has forced organisers to cancel the Cabramatta International Nines.
With temperatures expected to soar above 40 degrees in Sydney's west, medical professionals deemed it unsafe to stage the tournament.
The forced cancellation is particularly disappointing for teams from Japan, Turkey and Papua New Guinea who flew to Australia to take part in the tournament.
Thirty-two teams representing cultures around the world were set to play (26 men's, six women's), including what would have been Vietnam's first representative rugby league side.
Physical disability exhibition matches were also planned around what would have been the 18th annual edition of the Cabramatta Nines.
An NRL spokesperson said "our first and foremost priority will always be the health and safety of our participants.
"Cabramatta International Nines will be back again in 2021 and we thank everyone for their understanding."
Meanwhile, the NSW Blues had to scrap a children's football clinic in the bushfire-affected town of Batemans Bay due to Saturday's weather forecast.
"Uppermost in our minds is the welfare of the south coast community; and allowing them to devote their attention and resources to the risks they may be facing tomorrow is by far the most important consideration," NSWRL CEO Dave Trodden said.
"We are extremely sorry to disappoint the people in the area who were looking forward to the visit, but the safety of everyone in the area is paramount and our thoughts are with them."