The Tour Down Under took the unprecedented step of shortening a stage, with one team manager saying Tuesday's race was becoming a death march.
Bike computers were showing temperatures as high as the low 50s, thanks to the radiant heat off the road, during the opening stage from suburban Unley to Lyndoch in the Barossa.
Originally set for 145km, the stage featured three circuits of a finishing loop.
The laps made it easy for race organisers to cut one of them, shortening the race to 118km.
It is the first time a stage has been shortened since the Tour's start in 1999.
Australian sprint ace Caleb Ewan repeated his stage-one win at the same town a year ago and, for the second year in a row, he was also the Tour's first overall leader.
But the furnace-like conditions, which officially reached the low 40s, were the talk of the stage.
Ewan's Orica-Scott director Matt White has come to the Tour for many years as a rider and team boss.
"It was one of the hottest ones we have seen here for a long time," he said.
"It was a good decision by the race to shorten it by a lap as well.
"It was turning into a bit of a death march out there."
Early in the stage, riders' delegate Adam Hansen had about 20 colleagues come to him in the peloton - including some Australians.
Hansen consulted chief race commissaire Alexander Donike and director Mike Turtur.
"When I crossed the finish line, I don't think I could have done another lap," said Hansen, his Lotto Soudal jersey coated with salt from perspiration.
"It's definitely the hottest Tour Down Under stage I've done.
"It's probably the hottest road race I've done - I've done hotter mountain bike races."
It is not the hottest day in Tour history - and there have been years where the race has had a run of 40-plus days.
By contrast, the temperature is expected to settle to the low 30s for Wednesday's decisive stage through the Adelaide Hills.
But on a scale of one to 10, Turtur said Tuesday was "a solid eight".
Turtur had hoped the heat might subside as the race went through the Adelaide Hills on the way to the Barossa, but he said it was relentless.
"A lot of riders and managers have come up to me already and said it was a good call," he said of cutting the stage short.
"It's not rocket science - it was a sensible call.
"We've ridden through some tougher conditions, but the consensus today was doing another lap was going to achieve nothing.
"What's the point in cooking them (riders) for the rest of the race?"
