Victoria is in for a record-breaking heatwave, with the mercury set to soar to 47 degrees in some parts of the state.
Melbourne is expecting a top of 39C on Wednesday, while in the state's northwest, Bendigo is forecast for 42C and Echuca, Swan Hill and Mildura will reach between 43C and 45C.
A total fire ban has been declared for the Wimmera region and a heat health alert has been issued for northern Victoria.
State Duty Officer Greg Christison said temperatures will reach the low-to-mid-40s in the Wimmera and winds will increase.
"Tomorrow's conditions could make it difficult for firefighters to suppress a fire should one start, therefore we are asking people to take heed of the Total Fire Ban conditions," he said in a statement on Tuesday.
"People need to be aware of the increased fire danger and ensure your fire plan covers all possible contingencies."
A cool change will sweep through the state during the afternoon before temperatures soar again on Friday.
The state could record its hottest December day on Friday if centres in the northwest such as Mildura and Swan Hill reach a forecast 47C.
Mildura is forecast to swelter through three days in a row of 45C and above.
"That's only happened once before in 1939 so it is certainly a very significant heatwave, particularly for December," Bureau of Meteorology climatologist Dr Blair Trewin said.
The heatwave has already passed through Perth, which sweltered through three consecutive days above 40C at the weekend, while Adelaide is now racing its own four-day run of hot weather.
As Victoria cools down on Saturday, the heat will go up in the ACT and NSW.
Australian Associated Press