Schools and national parks have been ordered to close as parts of Victoria face the first catastrophic fire conditions since the Black Summer of 2019-20.
Tasmania, South Australia and Western Australia were also braced for extreme fire danger amid heatwave conditions.
Hot, dry and windy conditions were forecast across Victoria on Tuesday, with the possibility of thunderstorms and dry lightning.
A catastrophic fire danger rating had been declared for the Wimmera region, extreme in the Mallee, central and northern Victoria, and a high danger rating for rest of the state except for East Gippsland.
A total fire ban was in place for most of the state, including Melbourne.
The emergency management commissioner, Rick Nugent, said Tuesday’s weather forecast, with some areas predicted to reach 40C, would be challenging.
“We’re going to have an extremely hot, dry and windy day … followed by thunderstorms and lightning,” Nugent said on Monday.
“We are doing everything possible to make sure we are well prepared to respond to any fires that may occur anywhere in the state.”
The Country Fire Authority chief officer, Jason Heffernan, said conditions would be some of the most dangerous grass fire conditions since the Black Summer of 2019-20.
Black Summer was one of the most intense and catastrophic fire seasons on record in Australia.
Despite the catastrophic rating for Wimmera, he warned any areas from Melbourne to the west needed 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.
Tasmanians were also being urged to prepare for an increased fire danger over the coming days.
The Tasmania Fire Service deputy chief officer, Matt Lowe, said current weather conditions combined with a dry landscape meant fires could spread easily and become difficult to control.
“TFS are putting a temporary hold on issuing fire permits in the south and north of the state until 2am Thursday,” he said on Monday.
“While we are not declaring a total fire ban, we are asking people to think carefully before lighting campfires and using machinery, and if doing so please be extremely cautious.”
South Australians were also bracing for a hot and dry Tuesday and extreme fire conditions.
Total fire bans had been declared on Tuesday with extreme fire danger ratings for mid north, Riverland and Murraylands.
The South Australian Country Fire Service said “very hazardous” fire weather conditions were predicted.
The Bureau of Meteorology had also issued a heatwave warning for parts of Victoria, with conditions expected to ease with a cooler change from late Tuesday night through early Wednesday morning.
A severe heatwave warning was also in place for parts of Western Australia including Kimberley, Gascoyne, Central West and Great Southern districts.