Victoria is set to experience some of its worst fire conditions since Black Saturday, with most of the state expecting temperatures above 40C on Friday, as well as fresh northerly winds.
In Victoria's northwest, Mildura is tipped to have six days in a row above 40C.
Country Fire Authority (CFA) state duty officer Brett Boatman says abundant growth in the dry grasslands and drying forests mean there will be a very high fire danger.
He said conditions will be extreme in the southwest and very high in other areas.
"It is certainly one of the higher fire danger days I have seen since Black Saturday, no doubt," Mr Boatman told AAP.
"We have had a couple of quiet fire seasons and reasonably damp summer last year, a good winter, abundant growth, especially in the grasslands.
"There is a lot of fuel out there. So then you add that into the hot, dry weather we are experiencing at the moment; that brings together all the elements that bring about severe and extreme fire conditions."
Mr Boatman said it was likely there would be total fire bans, but he does not expect a code red day to be declared.
He said with a lot of people on holidays it was important they understand the conditions in the area they are in.
Melbourne is tipped to reach 39C on Friday, with Bureau of Meteorology senior forecaster Dean Stewart predicting many suburbs would likely hit 40C.
He said while Melbourne would have cooler weather on Saturday and Sunday, the change would not have any impact north of the Great Dividing Range.
Mildura's six-day hot spell will begin on Thursday and peak with a 45C day on Tuesday.
In the state's northeast Yarrawonga is expected to have five days above 40C.