The danger was said to be serious in Victoria and Tasmania but New South Wales has so far had the worst of the fires, the Australian Broadcasting Corp. reported.
Firefighters worked through the night to combat more than 100 bush fires in that state as hot, gusty conditions are forecast for Sunday.
More than 100 firefighters were working a blaze about 70 miles south of the national capital, Canberra.
A blaze near Yass, in southern New South Wales, has a 60-mile fire front, which a fire official said crews will be fighting throughout the night. Officials are concerned the westerly winds could push the fire into nearby towns.
No deaths have been reported. Six people have been treated for heat exposure, the BBC said.
Although temperatures in the region fell slightly Saturday, the average high daily temperatures across the country reached 104.5 degrees Fahrenheit this week, said David Karoly, co-author of a report issued this week by the Climate Commission.
The report blamed climate change for "increasing the risk of more frequent and longer heat waves and more extreme hot days, as well as exacerbating bushfire conditions."