Officials are rushing to set up a long-term base camp for hundreds of firefighters while more than half of Victoria is on high alert for extreme bushfire conditions.
The Wimmera region is slated to have catastrophic fire danger on Wednesday, while extreme fire danger is predicted for five of Victoria's nine total weather districts.
Temperatures are tipped to hit mid-30C to 40C across the state, with the Bureau of Meteorology forecasting the mercury to top 43C in Mildura in the northwest and winds of up to 40km/h.
More than 500 firefighters were still battling the Bayindeen blaze, northwest of Ballarat, on Monday.
The fire has burned more than 20,800 hectares and destroyed six homes along with sheds and fences.
The 131-hectare Victoria Park at Ballarat will become home to about 300 firefighters, potentially for more than a month, while the state contends with dangerous conditions, the City of Ballarat announced on Monday.
The base camp was slated to be set up before Wednesday with large marquees, laundry facilities, bathroom and kitchen facilities, and accommodation for firefighters.
The camp would act as a hub for crews battling blazes west of the regional city, the council said.
"The City of Ballarat is assisting Forest Fire Management Victoria and the Country Fire Authority to quickly establish a base camp before weather conditions worsen," it said.
Country Fire Authority chief Jason Heffernan on Monday said authorities were focused on the Wimmera region, with the fire risk modelled at the upper end of extreme.
The region had Wednesday's fire danger rating upgraded from extreme to catastrophic on Monday.
"At the moment the models are firming for at least a nasty day in six districts," he told ABC TV.
"Half the state is in extreme bushfire rating."
Other weather districts in the firing line are the Mallee, South West, Northern Country, North Central and Central.
Mr Heffernan warned residents in those areas they could not afford to be complacent and he particularly urged those who lived near bushland or grassland to clean up around the house.
"We need the Victorian communities to be ready for Wednesday," he said.
"The Bayindeen fire burnt under extreme conditions.
"We saw how quick that fire ran.
"We saw how far spot fires emerged, some 15km ahead of the main front."
The fire is not yet under control but firefighters have slowed its spread.
About 70 per cent of the blaze was behind containment lines as of Monday, with crews burning pockets of unburnt fuel between the fire front and the containment lines.
Watch and act warnings remained in place on Monday afternoon, with residents in Amphitheatre, Raglan, Elmhurst and Waterloo among those warned it was not yet safe to return to their homes.
An advice warning was also active for nearby towns although the threat had eased for parts of Langi Kal Kal, Trawalla, Beaufort, Lexton, Green Hill Creek, Rosyth and Lamplough.
Emergency Services Minister Jaclyn Symes said diverse terrain was making life difficult for firefighters.
"There's a lot of steep areas - there's private pine plantations," she told ABC Radio Melbourne.
"It is a difficult area to get into.
"The advice I have is that, even if it was perfect conditions, this is a fire that would take up to three weeks to fully extinguish."
The Victorian and federal governments are in talks about assistance for residents who have lost their homes or suffered property damage.
A man sparked four spot fires along the Western Highway at Buangor, not far from the bushfires, on Sunday by driving a car on its rims.
The 27-year-old Sebastopol man was seen driving on the wrong side of the road and almost hit a pedestrian before he was chased down by members of the public after dumping the car.
He has been charged and bailed to face court in mid-March.
