States have declared total fire bans across South Australia, Victoria and Tasmania ahead of the extreme heat. Adelaide's maximum temperature today is pegged to reach 41 degrees C, with 40 C on Friday, 41 C on Saturday and 40 C on Sunday, an ABC report said.
A catastrophic fire danger rating has been issued for the state's lower south-east, the report said.
Country Fire Service state coordinator Brenton Eden said "We are facing a horror day when we already have existing fires burning in the state."
Mildura in the state's north is expected to touch 40 degrees C for a week while southern parts of Victoria will also have a period of extended heat.