Victoria and Tasmania are facing statewide fire bans, with authorities warning conditions will be hot, dry and windy.
No fire bans have been implemented in New South Wales or the Australian Capital Territory at this stage.
The Bureau of Meteorology's Adam Morgan is asking people in the south-eastern region of Australia to take care.
Victorians have been told to stay inside, as parts of the state brace for the hottest day in nearly two years.
Acting Chief Officer for the Metropolitan Fire and Emergency Services Board in Victoria, Greg Leach, urged people to stay outside of the heat, as temperatures are forecast to each the early and mid forties.
He has told Sky News, authorities want to prevent any deaths.
