A hot air mass is pushing temperatures into the 40s across the country from the Kimberley region in Western Australia to Melbourne in the south.
While hot weather is not unusual in Western Australia, the Bureau of Meteorology has labelled it an "extreme heatwave" as the temperatures are unusually high.
The temperature at Fitzroy Crossing in the north of the state is expected to break records and hit 47 degrees on Saturday.
Local businessman John Rodrigues told Weatherzone that the town's 1200 residents are accustomed to the heat, but this would take its toll.
"You don't see that very often, normally we get up to 44C - so it is going to be pretty unbearable especially at night time when it doesn't cool down," he said.
Fires across Victoria
The heatwave has extended across to Victoria as firefighters battle an out-of-control fire threatening the town of Little River, west of Melbourne.
Residents are being told to evacuate, particularly those in Mambourin and Manor with firefighters warning failure to leave could be life threatening.
Melbourne is expected to reach 38 degrees while some parts of the state will swelter in 40-plus temperatures.
"It should go to high 30s and 40s and there might be some relief from the southwest over the afternoon as (a front) crosses central Victoria," Bureau of Meteorology senior meteorologist Peter Newham told AAP on Friday.
But strong winds, gusting up to 70km/h, are expected to continue into the evening before dropping off after 8pm.
Hottest summer in 24 years
That has prompted a total fire ban and warning from health authorities for some areas.
"The chief health officer has issued a heat health alert to notify you of forecast extreme heat conditions at or above heat health temperature thresholds," the government said in a statement.
The Bureau of Meteorology said the temperatures mean Victoria will record its hottest start to summer in 24 years.
"There is a change coming, every heatwave has to end eventually, however this is not a very strong change," senior forecaster Chris Godfred said.
"We should see it reach Melbourne very late on Friday night so unfortunately we're not going to get real relief from the heat until Saturday."
