The hottest start to a Victorian summer in more than two decades is expected to ease overnight, with forecasts pointing to a cool change.
Temperatures in most parts of Victoria on Friday soared to 40C, with Melbourne reaching 39C.
The heat was greatest in the state's western Wimmera and Mallee districts where Horsham and Hopetoun both reached 42C.
Avalon and Geelong both nudged just above 40C, breaking early December records for those towns since temperatures have been recorded, the Bureau of Meteorology said.
Melbourne's peak hovered between 37C and 39C.
"It's going to be a pretty warm night once again, 30s until midnight, hopefully dropping to 22 by sunrise," senior meteorologist Peter Newham told AAP.
The cool change is expected to hit the state's southwest from 5pm but Melburnians might not feel it until much later.
Milder temperatures over the weekend, plus light rainfall will give the state a break, Mr Newham said, before the weather heats up again mid next week.
Victoria's regional areas such as Mildura are still expected to reach 39C, but Melbourne is expected to reach a milder top of 27C on Saturday.
Sunday will be a bit cooler still, in the early 20s.
Most of the state can expect light rainfall and isolated thunderstorms.
"It is evident that summer has really hit the state of Victoria," emergency management commissioner Andrew Crisp said Friday afternoon.
About 19 bushfires had started in Victoria by mid-morning Friday, with the worst in the Little River area, southwest of Melbourne where an evacuation order was issued.
Police Minister Lisa Neville told Victorian parents to do the right thing by their children and avoid leaving them in a hot car.
The conditions have prompted a total fire ban in the Mallee, Wimmera and Northern Country, as well as a heat alert from the chief health officer.