SA's bushfire crisis mean the Tour Down Under might have to cancel a stage for the first time in the event's 15-year history.
Organisers must wait until Monday afternoon before they will know whether Tuesday's opening stage in the Barossa region can go ahead.
The Adelaide tour has never altered its route because of fire or weather, but race director Mike Turtur said there were serious doubts about the 135km first stage from Nuriootpa to Angaston.
A women's race is also scheduled for Tuesday in the Barossa area and this also could face cancellation.
"If it's a no-go zone for the Barossa, it's a no-go zone - simple as that," Turtur said.
"(It's) possibly the cancellation of the stage, depending on the advice from the correct people."
"Any activity in the region that's deemed to be dangerous to the public, then obviously you can't ask people to go into the area.
"It would be crazy to do that."
Turtur added that because of the logistics involved in holding a road race, it would be impossible to reschedule the stage.
If Tuesday's racing is cancelled, the Tour will start on Wednesday and run as planned through to Sunday.
The Barossa is threatened by one of four large fires burning in the state.
Adelaide and surrounding areas are coming off a brutal heatwave this week, with the temperature climbing well into the 40s.
The riders will have easier conditions next week, with forecast temperatures in the high 20s and early 30s.
But the problem for fire authorities and the Tour organisation is strong winds, which make it impossible to predict what the fire front will do.
Star Australian rider and two-time Tour winner Simon Gerrans said the cyclists would adapt if stage one does not go ahead.
"You just move onto the second stage, everyone is in the same situation," Gerrans said.
Riders have been Adelaide through the last week preparing for the Tour.
Gerrans and Tour de France winner Cadel Evans said they had trained as early as possible in the day to avoid the worst of the Adelaide heatwave.
"I'm from Victoria and the first hot day we had was a week ago," Evans said.
"So I've suffered this week as well.
"By the looks of it, there will be much friendlier conditions for the race.
"We've had a wet, rainy summer, so I'm hardly ready for the heat.
"I'm not going to complain about that, but it's fairer for the Europeans of course who are coming from winter."