A bushfire has damaged a home, several sheds and fencing in Melbourne's south-east, but firefighters say homes are no longer threatened as a cool change sweeps through.

On Saturday afternoon the blaze was burning dangerously close to homes at Carrum Downs and residents were told to evacuate.

Loading

Two aircraft were sent to the fire at Blue Wren Rise, which was burning in a south-easterly direction towards Lexton Drive.

The CFA's assistant chief officer for the region, Trevor Owen, said 200 firefighters were likely to remain in the area overnight, but properties were no longer being threatened.

"We've had one property which has sustained some fairly significant damage where some embers have come in through the roof, through an evaporative cooler," he said.

"There is also some fencing at the back of those properties and we've also sustained some damage to four sheds."

At 9:00pm the CFA said the fire had been downgraded to advice level, with crews continuing their efforts along Valley Road to extinguish any hot spots, and continuing to patrol overnight.

Temperatures across much of Victoria exceeded 40 degrees Celsius on Saturday, but a cool change saw the temperature in Melbourne's CBD plummet by more than 10C in less than 10 minutes — from 41.4C at 5:50pm to 28.8C at 5:56pm.

Robert Woods, who lives near where the blaze was burning, resisted pressure to evacuate at the height of the fire.

"I'm terrified. I've got to tell you. I'm terrified. I've never seen it come this close before. I'm really terrified," he said

"I've got my animals ready, evacuation papers, the legals, all that stuff is ready to roll.

"I don't really want to leave and I don't think I will but certainly the animals will be taken care of because my partner will take care of that."

A bushfire burning close to houses at Carrum Downs ( ABC News )

Mr Woods said he wanted to hang around "to the very last minute" because he was confident the CFA "could fix this".

"We just hope they'll be able to bring this under control so we can relax a bit because I'm almost sick," he said.

"The whole house is just getting wet right now front and back and if I have to I'll take an axe to the water tank and let it flood everything."

Residents were told to evacuate to the Carrum Downs Shopping Centre and a woman there said with the imminent threat, she made an easy decision.

"It was get the dog, get the cat, get the kids, get out. Easy," she said.

Temperatures reached 45C at Mildura, 44.6C at Hopetoun Airport in the Wimmera, 42C at Viewbank and 41.7C in Melbourne.

The heat led to a number of drownings and near-drownings in Melbourne and about 50 fires were reported across the state.

A home was damaged when embers entered through the roof. ( ABC News )

Why wasn't an emergency warning issued?

Emergency Services Commissioner Craig Lapsley was asked at a media briefing why an emergency warning had not been issued for the Carrum Downs fire.

"Even though there may be structures alight, or there may be fences alight or outbuildings that's something the incident controller will determine about what is the immediate threat versus the immediate threat to life and injury," he said.

"Obviously that's a dynamic environment.

"The emergency warning is where there is imminent danger to your life.

Mr Lapsley also expressed concern that many people had been using barbeques in coastal areas in defiance of the total fire ban.

Thick dark smoke covered the area from the out-of-control fire. ( ABC News )

"The message has to be not to use inappropriate barbeques. Solid fuel barbeques on a total fire ban day are illegal," he said.

"It needs to be a properly constructed barbeque, gas or electric."

Fires were also burning in other states, with an emergency warning issued for a fire in South Australia's Upper South East, amid catastrophic conditions in that state.

People were being advised to open up their houses as the cool change came through.

"Our houses will remain hot. Make sure you open them up and get that cool breeze through them as quickly as possible," Mr Lapsley said.