Authorities have issued a total fire ban for most of Victoria on Saturday as soaring temperatures are set to scorch the state.

The Country Fire Authority has set tomorrow's fire danger rating as extreme across central and western Victoria.

It comes as temperatures are forecast to reach a top of 37 degrees Celsius across parts of the state on Saturday.

Meteorologist with the Bureau of Meteorology (BOM) Keris Arndt warned Victorians that Saturday would be the most significant day of fire danger the state has seen this year.

"We're expecting extreme fire dangers through the Wimmera, South West and North Central districts and high fire dangers across all other districts in Victoria," he said.

It comes as BOM has issued a severe weather warning for damaging wind gusts of up to 90 kilometres per hour in elevated parts of central Victoria.

He said Victoria was in for a scorcher tomorrow.

"We're looking at a very hot day for this late in the season. Generally across the state we'll see temperatures rise to the high 30s to low 40s," Mr Arndt said.

"In Melbourne, we're looking at 37 degrees. If we reach that 37C, it's the latest in the season we've seen temperatures reach that high since 2007."

Hot and gusty conditions are expected to extend across the state from the south west to central areas by mid-morning before easing in the afternoon.

Deputy Emergency Management Commissioner Chris Stephenson asked people not to travel to high risk areas on Saturday, to enact their fire plans and stay across emergency broadcast information.

"Our fire agencies are prepared but we need our community prepared too."

Mr Arndt said a cool change is expected to shift across the state from the south west in the early afternoon, reaching the Melbourne area around 5pm.

"We'll see temperatures drop by potentially about 10 or 15 degrees, depending on the time it comes through, in the period of about an hour, so it could be quite a relief to the heat," he said.

Fires may be 'dangerous and exceptionally fast'

CFA Chief Officer Jason Heffernan said there were four bush and grass scrub fires burning across Victoria with 50 firefighters working to extinguish them with the help of 17 water bombing aircraft.

He said the total fire ban extends over the Mallee, Wimmera, South West, Northern Country, North Central and Central districts.

That means from tomorrow, camp fires will be forbidden and anyone who has already lit a fire has been asked to extinguish it using water, not soil.