According to the meteorology bureau, the overnight temperature did not drop below 25.3 degrees Celsius on Saturday through Sunday in central Sydney, making it the hottest November night since records started.
By 4:30 a.m. on Sunday, the temperature had already reached a scorching 30 degrees Celsius, before hitting over 40 degrees for the second consecutive day.
"New South Wales is already experiencing a severe heatwave with very hot conditions yesterday, and today is a repetition of some of those conditions," said Agata Imielska of the Bureau of Meteorology.
November's daytime records dropped elsewhere in the southeast of Australia, with Saturday's outback towns of Griffith and Mildura touching 43.2 and 45.7 degrees Celsius, respectively.
The heatwave saw bans on lighting fires imposed across large swaths of the state of New South Wales (NSW), which during the last southern hemisphere summer was badly affected by devastating bushfires.
A number of blazes broke out on Sunday, including one that the NSW Fire and Rescue Service said destroyed property on Sydney's western outskirts.
More than 60 bushfires were still burning in the state, but most were brought under firefighters' control as a shift in southerly wind led to a rapid drop in temperatures.
Since the catastrophic 2019-2020 fires, which destroyed an area roughly the size of the United Kingdom and left 33 people dead while tens of thousands fled their homes, this was the first burst of major bushfire violence.
The fire season also destroyed or displaced almost three billion animals and cost an estimated US$7 billion to the economy.
The new heatwave comes only two weeks after government scientists warned that the country dependent on fossil fuels should prepare for more to come, forecasting that climate change will continue to worsen Australia's bushfires, droughts, and cyclones.
The link between climate change and bushfires has been consistently played down by Conservative Prime Minister Scott Morrison, and he has committed to keeping Australia one of the world's leading exporters of fossil fuel.
But Australians are deeply worried about climate change, with almost 90 percent believing it is a crucial or major danger in a recent survey by Sydney's Lowy Institute.