Fires forced the evacuation of up to a dozen villages in the Snowy Mountains in New South Wales.
In the federal capital Canberra, the cost of the 18 January fires which destroyed 530 homes has been raised to A$250m ($150m), making it the country's second-worst bush fire disaster.
With temperatures around Canberra reaching 40 degrees Celsius and the wind strong and gusting, fire authorities said outlying settlements again faced extreme danger.
Police in Canberra charged a 16-year-old boy with lighting bush fires, the third person to be charged with arson since the city was hit.
'Own weather'
The bushfire in Victoria was so intense that it was creating its own weather system, local firefighters said.
"It has its own convection current. The ferocity... is creating lightning over the northern and south-eastern flanks," said Lyndel Hunter of the Victoria Country Fire Authority.
Four buildings, at least two of which were homes, were destroyed in Omeo, a gold mining town 400 kilometres (250 miles) northeast of Melbourne. More than 3,600 livestock were killed in the blaze.
"It was hot, windy, smoky and very scary," Omeo resident Judy Smith told Associated Press news agency. "It's been like a war zone," she said.
The fire was reported to be moving towards the nearby town of Mitta Mitta.
Three more homes were lost in a fire on the outskirts of Sydney which closed down the main southern route into the city for two hours.
Dozens of other fires are burning between Canberra to the Gippsland region in Victoria state - an area stretching 300 kilometres (185 miles).
"This is one of the worst days we've had since the fires began," said Kevin Monks, a spokesman for Victoria's Department of Sustainability and Environment.
Further north, New South Wales fire chief, Phil Koperberg, said that fires burning through mountain forests were approaching the regional centre of Jindabyne from three sides, and up to a dozen villages have been evacuated.