A blaze in the state's bushfire-ravaged East Gippsland region flared up on Thursday, prompting an emergency alert as it threatened lives and homes.

Temperatures reached the high 30s across the state on Thursday and will rise further on Friday, as high as 45C in northern regions.

Melbourne is expected to reach 43C on Friday afternoon, according to the Bureau of Meteorology's latest forecast.

Melburnians have been urged to be aware of potential changes to public transport due to the heat.

"Tomorrow we're going to see increased humidity, and that's going to lead to oppressive conditions thanks to a tropical plunge moving across Victoria," Bureau of Meteorology senior forecaster Diana Eadie said.

"It's going to feel for some parts more like a build-up day in Darwin rather than what we're accustomed to in Melbourne."

The energy market operator has issued a level-two warning for Victoria on Friday, but at this stage expects no impact on the power supply.

A spate of hot days is forecast to extend from Thursday into the weekend, raising fire danger levels ahead of damaging northerly winds and rain through the state on Saturday and Sunday.

But the rainfall is not expected to fall evenly across the state.

"We'll see that rain move across, or showers and storms tending to rain areas. Though it will still be patchy and hit-and-miss, so not everywhere will see that drop of rain," Ms Eadie told reporters.

"With the incredible amount of humidity, risk of locally heavy falls and flash flooding will extend across much of southwestern and central parts again on Saturday, including the Melbourne area."

It has prompted a total fire ban for all state regions except Gippsland and the northeast.

Those bushfire-ravaged areas will not be affected by the fire ban, but still have nine of the 10 currently active fires burning more than 1.5 million hectares in Victoria.

Emergency services say these alerts were put in place in an effort to prevent new fires across forested and grassland areas, particularly in the west of the state.

Emergency Management Commissioner Andrew Crisp urged Victorians to remain vigilant, sending a blunt reminder that the fire season was far from over.

"We've had the benefit of some suppressed, benign conditions over the last few days. However, as we've heard, it's going be hot," Mr Crisp said.

"We've had fires the last two years in March, where we've lost property in this state. So, we have still got probably another six to eight weeks to go in relation to some fairly active fire behaviour."

Emergency services and defence forces have continued clearing roads to fire-affected communities.

About 250 people were able to return to the stranded town of Mallacoota, where emergency minister Lisa Neville warned locals they might see embers and smoke as fire activity increased on the weekend.

Australian Associated Press