Firefighters battled scores of wildfires in southeastern Australia as temperatures soared to 45 degrees Celsius in some areas.
Authorities evacuated national parks and warned that hot, dry and windy conditions were combining to raise the threat to its highest alert level.
"You don't get conditions worse than this," New South Wales Rural Fire Service Commissioner Shane Fitzsimmons said.
"We are at the catastrophic level and clearly in those areas leaving early is your safest option."
Catastrophic threat level is the most severe rating.
Wildfires are common during the Australian summer.
The combination of soaring temperatures and dry, windy conditions since Friday have sparked fires that burned 20,000 hectares (50,000 acres) of forests and farmland across southern Tasmania.
In New South Wales, Australia's most populous state, the fires scorched more than 30,000 hectares (74,000 acres).
All state forests and national parks were closed as a precaution and total fire bans were in place.
In Victoria state, where fires in February 2009 killed 173 people and destroyed more than 2,000 homes, officials said two people were treated for minor burns and four were treated for smoke inhalation.
No deaths have been reported
Around 100 houses, the majority on the island state of Tasmania, have been destroyed by bushfires in recent days, and many people are still missing in fire-ravaged areas.
Police said no bodies were found during preliminary checks of the ruined houses.
Wildfires have razed 20,000 hectares of forests and farmland across southern Tasmania since Friday.
One volunteer firefighter suffered severe burns to his hands and face while fighting a grass fire near Gundaroo village, about 220km southwest of Sydney, the New South Wales Rural Fire Service said.
He was flown to a hospital in Sydney for treatment.