Victorians are being urged to stay on alert and keep abreast of fire updates during Thursday's forecast extreme heat.

Severe fire danger is forecast for most of the state as temperatures are expected to reach into the high 30s in the south and into the 40s in the north.

Authorities are warning any fires that break out will move very quickly.

Premier Ted Baillieu says Victoria is extremely dry and the risk of fires is significant.

"If there is a fire, then the prospect of that fire running fast and running intensively is also significant," he said.

"It's obviously important that everybody take full measure of the circumstances they find themselves in, pay attention to all communications, and I say all communications."

Fire Services Commissioner Craig Lapsley says the state is in a good position to deal with any potential fires.

He says every fire that has started in the past couple of days has been quick to be managed and controlled.

"That means that we move into Thursday with no fires of significance on the board, no fires that we've got major resources at," he said.

"That means we have all our trucks back to the stations and all our helicopters and fixed air assets available for deployment.

"We do not want to have going fires on the list starting Thursday."

Mr Lapsley says the Elvis aircraft is also back in action after undergoing repairs.

He says central Victoria shows the potential of fire intensity of significance by 3pm on Thursday.

A total fire ban has been declared for the Wimmera, South West, Central and North Central districts.

Meanwhile, electricity company Powercor says it will go ahead with planned maintenance work on Thursday, leaving 400 customers in the Daylesford area without power on a severe fire danger day.

Spokesman Drew Douglas is assuring residents the company has consulted fire agencies and the community.