The city of Sydney recorded its hottest day on Sunday with the mercury hitting 47.3 degrees Celsius after nearly 80 years, according to Australian weather authorities.
Temperatures were expected to remain in the high 30s to early 40s Celsius Monday and the fire ban would be continued, it said.
Emergency services are bracing for what is predicted to be one of the hottest days of the year as a unsafe "blast furnace" moves across Australia.
Authorities say the hot conditions are not expected to ease until Tuesday.
The hottest temperature ever recorded in the area was 47.8 Celsius degrees (118.04 Fahrenheit) in 1939, the Bureau of Meteorology for the state of New South Wales (NSW) said.
So, while brutally cold temperatures hit the United States, emergency services in Sydney prepared residents on the other side of the equator for dangers of a different sort.
Inner Sydney didn't get quite as hot as the western suburbs.More news: Golden Globes 2018: Stars take activists as dates on red carpet
Thursday will reach a weekly high of 32 degrees in Adelaide with a shower also possible. Temperatures peaked at 42C on Saturday, before cooler air pegged the heat back to a more comfortable 21 degrees on Sunday.
An afternoon breeze helped cool the city a few degrees.
Canberra will be hot and sunny today with a high of 39 degrees.
Officials issued a fire ban for the region.
Extreme heat and fire risk warnings have been issued for Victoria, South Australia, New South Wales and Tasmania. Residents of Carrum Downs on the southern outskirts of Melbourne were evacuated from their homes on Saturday as a bushfire edged closer, local media reported.
About 400 homes lost power and 50 fires were reported across Victoria on Saturday, although many were small and were extinguished, Reuters reported. The NSW Rural Fire Service said the fire danger rating in both areas was "severe".
Other states in the southeast of the country were also forced to suffered through the hellish weather, with conditions in some parts of Victoria so bad on Saturday, a 10-km stretch of the Hume highway began to melt under the scorching summer sun.