Schools and national parks will close as Victorians brace for catastrophic fire conditions for the first time in five years.
Hot, dry and windy conditions are forecast across the state on Tuesday, with the possibility of thunderstorms and dry lightning.
A catastrophic fire danger rating has been declared for the Wimmera region, extreme in the Mallee and high danger rating for rest of the state except for East Gippsland.
A total fire ban has been declared for the Mallee, Wimmera and Northern Country regions, with the mercury tipped to reach 40C in Mildura, Ouyen and Birchip.
Late on Monday, the Total Fire Ban was extended to regions including Central, South West and North Central due to weather modelling and grassland curing conditions.
The ban means no fires can be lit in the open air between midnight on Monday and midnight on Tuesday.
Emergency Management Commissioner Rick Nugent said Tuesday's weather forecast would be challenging
"We're going to have an extremely hot, dry and windy day ... followed by thunderstorms and lightning," Mr Nugent said on Monday.
"This increased fire risk has resulted in a catastrophic fire danger rating for the Wimmera region.
"This is the first time since November 2019 that we've had a catastrophic fire danger rating.
"We are doing everything possible to make sure we are well prepared to respond to any fires that may occur anywhere in the state."
Country Fire Authority chief officer Jason Heffernan said predicted conditions would be some of the most dangerous grass fire conditions since the Black Summer of 2019-20.
"Fires that start and take hold under catastrophic conditions can grow large very, very quickly," he said.
"It can not be understated how challenging those conditions can be for our firefighters - and we need the community to do their bit."
Despite the catastrophic rating for Wimmera, any areas from Melbourne to the west need to be alert to fire.
"Grass fires can be just as deadly as bushfires during the 2019-20 season, they move incredibly fast and can jump roads," he said.
Victorians are warned to avoid unnecessary travel to areas under the catastrophic fire danger declaration, with Forest Fire Management Victoria moving to close national parks in those regions and ask those who are already camping on public land to leave by Monday night.
The Bureau of Meteorology has also issued a heatwave warning for parts of the state, with conditions expected to ease with a cooler change from late Tuesday night through early Wednesday morning.