Fatigue is the new challenge facing the worst-affected communities, having sweltered through a week of 45C-plus days.
Thursday tested longstanding heat records for communities across South Australia's north, with the outback town of Marree reaching 49.8C.
About 685km north of Adelaide, Marree was the hottest spot on the planet for a day, according to online world temperatures site El Dorado Weather.
Warren Smith from Marree Roadhouse told AAP it was a "mixed honour", adding conditions on Friday threatened to be just as severe.
"It's shaping up that way again today. It's really not pleasant out there," Mr Smith said.
While 49.8C was the official maximum recorded on Thursday, Mr Smith said his car's thermometer showed 50C.
He said residents had grown accustomed to high heat, with many heading south to avoid the worst of the summer conditions.
For those who stayed, he said this season had been unlike any other in recent memory.
"It's been a bit relentless. People are starting to get a bit fatigued," Mr Smith said.
Roxby Downs recorded 49.6C, while Woomera hit 48.5C and Leigh Creek climbed to 48.2C - all temperatures never before seen.
Casey Bowie, who moved to Roxby Downs from Townsville last week, told AAP she had never experienced heat like Thursday.
"It feels like you've opened the oven on fan force and just let it blow straight into your face," Ms Bowie said.
"It's not uncomfortable like it is in Queensland. It's painful," she said.
Ms Bowie confessed conditions were so extreme on Thursday, she considered searching for a flight back to Queensland.
While morale remains high, she said the heatwave had become a test of endurance.
"We're all completely wrecked at the end of the day, even if you haven't done that much," she said.
"After a week, it just starts to take it out of you."
Senior meteorologist Dean Narramore said the blistering heat had broken dozens of temperature records across South Australia, NSW and Victoria.
He said what made this event more unusual was its longevity, which meant there was more time for heat to build up.
"This situation had a bit of a blocking pattern," the Bureau of Meteorology forecaster told AAP.
"So the heat has just sat over us and just kind of wobbled around the southeastern part of the country (with) no strong cold front to come in and clear it out."
Mr Narramore said the records that had been broken were multigenerational, with some having stood for a century.
"They're not just 10 or 20 years old - they're 30, 50, 80 and in some cases 100 years old," he said.
"A lot of the records have been similar to a heatwave back in 1939, so that's going back a long way."
Heatwave warnings remain in place for NSW, Victoria, Queensland, WA, SA, the ACT and NT on Friday.
More heatwaves could be in store this summer, with the whole of February and March to come.
Mr Narramore said average temperatures in Australia were one to one and a half degrees higher than they were a century ago.
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