Smoke from the tragic bush fires could halt play in the third cricket test between New Zealand and Australia.
The test begins in Sydney on Friday with the highest temperature for the five day match predicted to arrive on Saturday.
"With that second very hot spell, we would expect to see a continuation of smoke haze and poor air quality into the weekend, if not further," the local weather office has warned.
A player involved in a recent Sheffield Shield game likened the "shocking" and "toxic" playing conditions at the SCG to smoking 80 cigarettes a day.
There are discrepancies between different sports bodies over what constitutes hazardous conditions but there is a real possibility of play having to be halted.
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Nine people have died in the bushfire disaster and millions of hectares of land have been burned since August.
According to CricInfo, the ICC guidelines say umpires can stop a game when the Air Quality Index hits 300, but the Australian Institute of Sport mark is 150 for intense activity.
There are not only health concerns, but the smoke can make it hard for players to see the ball.
A Big Bash game in Canberra was abandoned last weekend and a domestic game at the Sydney Cricket Ground, venue for the test, was affected by a thick haze this month.
Cricket blogger Rick Eyre likened the SCG situation to "the apocalypse" while a CricInfo writer urged the cricket bosses to call the game off.
Cricket Australia's head of operations Peter Roach has conceded that the umpires might be forced to take the players off the field at some stage.
"What we've seen in Sydney and Canberra is that it comes to a point where it becomes a challenge. Rules are in place, like rain, to add time for suspended play," he said.
"What we are finding is that it can come in quick, but it can also go quick so it's unlikely it will be there for a full day. We might see some challenges across that day, but we'll play it like rain or adverse weather. What we've seen is about one day in ten is proving a challenge, we hope it won't come during the Test but we also understand that it might.
"We have concerns when the smoke is around because it is a challenge on those two metrics: visibility and breathing."
Fox cricket commentator Mark Howard said it was "frightening what people are going through in this part of the world" after the Canberra game.
Sydney Thunder coach Shane Bond, the former Kiwi fast bowler, told the Daily Telegraph the umpires made the right call.
His opposite Jason Gillespie said: "Being able to see the ball is pretty fundamental in our sport but also I think the respiratory situation is something that needs to be considered."
New Zealand coach Gary Stead said the Black Caps would be bound by the playing conditions. CA had protocols in place and he was sure the right action would be taken. He did not know of an asthmatics in the Kiwi side.
NSW spinner Steve O'Keefe said being out on the field during the affected Sheffield Shield game at the SCG was like "smoking 80 cigarettes a day".
"The one thing they need to look at is the air-quality policy," O'Keefe said. "That was shocking. I don't have kids, but if I did they'd be locked up inside, and if I was at home I wouldn't be training or playing in it.
"I tip my hat to Queensland because when you're behind in the game you've got a reason to whinge, but they got on with it.
"That air quality was shocking. The doctor was all over it and speaking to us about it, and the fact the game wasn't going to go all day was considered, but in the future they need to look at it because it's not healthy — it's toxic."