Melbourne is set to swelter through its hottest day in two years as the state faces a "killer" heat event and extreme bushfire risk, authorities warn.
People have been told to stay inside on Saturday, with Melbourne forecast to reach 41C, and temperatures in regional areas into the mid-40s alongside winds of up to 40km/h.
"This heat is a killer. It's going to be like a blast furnace tomorrow and you need to adjust what you do," Ambulance Victoria's state health commander Paul Holman told reporters on Friday.
"You need to take this seriously. You need to take care. So put off the sporting events, put off the outside events, stay inside."
Saturday is set to be Melbourne's hottest day since January 13, 2016, when temperatures soared to 42.2C.
Geelong and Bendigo are forecast to reach a high of 42C, Swan Hill, Echuca and Warracknabeal 43C, and Mildura is expected to hit 44C.
The extreme heat warning comes as authorities plead with parents not to leave kids in cars, following the release of figures showing 1696 kids were rescued from vehicles in the 12 months to August.
"I know today, unfortunately, I'll go back to my office, and I will look at the stats and I will see children left in cars today," Mr Holman said.
A statewide fire ban has been issued for Saturday, with extreme fire warnings in the Mallee and Wimmera, and severe warnings in southwest and central parts.
"If a fire starts it will run, it will run hard and has the potential to do significant damage," Emergency Management Commissioner Craig Lapsley said.
"On these days the conditions can beat the crews and the terrain.
A cool change is expected to reach Melbourne in the late afternoon to early evening, with temperatures potentially dropping 20 degrees over several hours.
But Mr Lapsley said the danger wouldn't necessarily be over.
"We know in Victoria, that's the devastating time of the fire. When it changes direction ... we see fires progress, sometimes triple their size," he said.
Residents are urged to have their fire plans ready, while people travelling throughout Victoria need stay on top of the conditions in their area.
The extreme weather is not expected to lead to blackouts but contingency plans are in place, Deputy Premier James Merlino says.
