“The conditions were extreme yesterday. They’re catastrophic today,” Heffernan said.
Temperatures in Melbourne are expected to hit 42C on Friday and while areas in north-west Victoria may reach 45C, a cool change is forecast in the south-west.
A bushfire near Longwood, central Victoria, has burnt through nearly 36,000 hectares, authorities said, with at least 20 homes in the small town of Ruffy destroyed.
Ruffy CFA captain George Noye said the town had been “severely” affected.
“The main street looks like a bomb’s gone off, we’ve lost a school,” he told the ABC.
“Some properties have lost everything. They’ve lost their livelihoods, they’ve lost their shearing sheds, livestock, just absolutely devastating.
“But thankfully, at the moment, no lives have been lost.”
A statement from Victoria’s state control centre on Friday said the Longwood fire was “incredibly dynamic, with the fire spreading in multiple directions” and may spread further than initial estimates.
Victoria Police Deputy Commissioner Bob Hill said three people – two adults and a child – remain unaccounted for in the Longwood area.
He said authorities spoke to them yesterday at their property, warning them to seek shelter as it was too late to evacuate. Fire officials returned later to find the home had burnt down but could not locate the three people.
“They may be safe, they may be alive, let’s not get ahead of ourselves, but we are keeping an open mind,” Hill said.
In the Australian Capital Territory, which includes the capital Canberra, a total fire ban was declared for the first time in six years.
Sydney will see the mercury rise up to 42C on Saturday, before dropping to around 26C by Sunday.