More than 2000 firefighters battle hottest November day in 125 years

Firefighters battled more than 60 blazes across Victoria as the state recorded its hottest November day in 125 years.

Six families had to be evacuated from their homes and three structures – possibly including one house - have been destroyed.

Emergency commissioner Andrew Crisp said police were investigating a number of fires that they suspected were deliberately lit.

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Across the state, more than 2000 firefighters are battling the conditions, supported by more than 200 trucks and 33 helicopters and aircraft.

"We will continue to commit significant resources to fighting the fires," Commissioner Crisp said.

He said a cool change had started making its way across the state, but that dry lightning continued to pose significant dangers.

Bureau of Meteorology forecaster Kevin Parkyn said that in 30 years as a meteorologist he could not "remember a day like this in November".

"If you think back to Sunday the temp was 16 … today it was 40.9 in the city," he said.  

"We have to go searching through the record books pretty hard to find a day when we recorded a temperature like that in Melbourne. In fact, 1894."

Melbourne's overnight minimum temperature was 26 degrees, which is the warmest evening since 1901, when the mercury didn't dip below 26.2 degrees.

Swan Hill and Kyabram recorded the highest temperatures in the state, peaking at 43.6 degrees. It reached 42.4 degrees in Laverton and 41.4 in Bairnsdale.

A cool change fuelled by a south-westerly wind had moved across the state with some regions recording a 15-degree drop in temperature in as many minutes.

Wind gusts reached 130km/h, with 117km/h recorded over Port Phillip and 104km/h at St Kilda.

Power outages across the state are now affecting more than 100,000 people.

More than 80,000 customers are without power in the western part of the state, with Geelong, Bendigo and Ballarat hardest hit, service provider Powercor said.

Emergency Services Minister Lisa Neville defended her government's fire season preparation, but pointed to a diminishing window for backburning brought on by lengthening fire seasons.

"Today we have seen, I suppose, some of the worst conditions that you would expect to (see) in February or March and we're seeing in November," Ms Neville said today.

"So, you've got fire conditions, you got your heat, you've got the incredible wind gusts, both at the hot winds through to the cold winds, the dust that you've seen."

An out-of-control bushfire in Bonn and Strathallan is threatening homes, with residents told it is too late to leave. It is in the area declared code red.

"You are in danger, act now to protect yourself. It is too late to leave. The safest option is to take shelter indoors immediately," the warning states.

The fire danger rating is severe or very high for the rest of Victoria, with damaging winds also expected across the state.

It's also the first time this season a statewide total fire ban has been issued.

Crews are responding to more than 22 fallen powerlines, and 130-plus separate faults across the state which are being impacted by the extreme winds.

"Due to the number of faults, extreme weather conditions and the need to be able to restore power safely, restoration times may be longer than usual," a statement says.

Earlier, Premier Daniel Andrews said it was going to be a "long and challenging day" for the state's fire services, and power disruptions weren't about supply.

"It's nothing to do with the power we've got, it's much more to do with the network... it's not a supply issue, it's about transmission," he told reporters.

All public parks in the code red areas are closed, and more than 200 schools and early learning childhood centres are closed across the state.

Health officials also warned the pollen count would be "extreme", coinciding with the third anniversary of the thunderstorm asthma event, which claimed 10 lives in 2016.