State braces for hottest Australia Day in history© Nine

Hundreds of people have fled their homes as resurgent bushfires continue to rage in Victoria during a sweltering long-weekend heatwave that could see the worst fire conditions in almost 20 years.

There are currently 12 fires burning throughout the state, with the blaze at Otways in the state’s south-west one of the longest-burning.

After erupting a couple of weeks ago, the fire broke containment lines on Saturday afternoon, and has been closing in on the town of Gellibrand.

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Multiple bushfires are burning in Victoria.© 9News

Fire authorities in Victoria asked residents across the state to heed emergency service warnings, as extreme-to-severe heatwave conditions cause bushfires in the landscape to flare.

“We have not seen severe to extreme intensity heat wave conditions like we are going to experience over the next seven days since 2009,” Emergency Management Commissioner Tim Wiebusch said.

“Take heed of the warnings, look after yourself, look after your family, those that are vulnerable.”

Hundreds of people fled their homes for nearby relief centres, with reports one property has been lost to the blaze.

Other fires continue to burn in the state’s north-east.

Multiple “watch and act” warnings have been issued by Vic Emergency, including some “leave now” warnings for the fires that continue to burn near Walwa.

Peak danger is expected tomorrow, with extreme heat forecast in the state’s north, though the rest of the week is also of concern with multiple days of 40 degree temperatures anticipated.

Hundreds have been evacuated from their homes© 9News

Heatwave sweeps country

Millions of Australians are set to swelter through blistering heatwave conditions on Australia Day and early this week, putting authorities on high alert.

Temperatures are soaring across south-eastern parts of the country today, with the mercury heading into the high 30s and beyond in Brisbane and Adelaide.

Temperatures in Adelaide should soar to 45 degrees today, while inland parts of South Australia could reach 48 degrees.

Annual Adelaide Australia Day event The Aus Lights on the River and the evening fireworks have been cancelled because of the heat. Usually about 25,000 spectators take in the annual event.

Brisbane hit a high of 35 yesterday before creeping up to 37 degrees for Australia Day, while Sydney should top out at 27.

Melbourne should have a brief reprieve from yesterday’s heat before shooting back into the mid-40s tomorrow.

Canberra nudged 40 degrees yesterday afternoon – the hottest capital in the country.

Emergency services were forced to issue an urgent reminder not to leave children, pets or older people unattended in vehicles after paramedics responded to 11 cases of children locked in hot cars across Melbourne and regional Victoria.

Victorians are set to swelter through heat wave conditions with temperatures to soar into the 40s this long weekend.© 9News

“The temperature inside a vehicle can double and become deadly within minutes,” Ambulance Victoria Director of Emergency Management Dale Armstrong said.

“It is particularly dangerous for children to be left inside vehicles, as a child’s body temperature rises three to five times faster than an adult.”

The mercury surpassed 38 degrees in Melbourne on Saturday, while temperatures soared beyond 46 degrees in parts of northern Victoria.

The city is headed for a top of 44 degrees on Tuesday, while northern parts of the state could hit record-breaking highs of 48 degrees.

“If you are on the coast you will see a bit of relief coming through on Tuesday, but that does mean we are expecting some very hot days on the way,” Bureau of Meteorology’s Jonathan How said.

“Anywhere inland, unfortunately relief only comes at the end of the week, even into next weekend, so we are looking at a run of five to seven days above 40 degrees and some locations even above 45 degrees, even pushing towards 50 degrees.”

While Australians on the east coast prepare to sweat through the week, those in the west are dealing with the impact of a second tropical cyclone in a matter of weeks.

Tropical Cyclone Luana made landfall as a Category 2 system when it made landfall along the Dampier Peninsula north of Broome.

Wind gusts up to 106km/h were recorded north of Broome, in Lombadina, along with more than 100 millimetres of rain since midnight on Saturday.

The storm has since weakened to a category 1 system moving inland.

Residents along the Kimberley coast should expect heavy rainfall and damaging winds over the long weekend, which is only expected to ease from Tuesday.