Several temperature records could be broken as parts of the south-east will reach close to 50 degrees.
Several parts of Australia's south-east have soared above 40 degrees as a heat wave smashes Victoria and South Australia.
Adelaide will hit 45 degrees later today, which has led to several Australia Day events in the city being cancelled.
The Aus Lights on the River and the evening fireworks have been cancelled because of the heat; usually about 25,000 spectators take part in the annual event.
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The mercury will remain above 40 degrees tomorrow, with the city of churches set to experience maximum temperatures above 30 degrees all the way until Saturday.
Ceduna on the state's coast is expected to reach 47 degrees this afternoon, according to the Bureau of Meteorology.
Parts of Victoria are also set to swelter, with Melbourne reaching 44 degrees tomorrow, and parts of the state getting close to 50 degrees.
Mildura in Victoria's north-west is expected to have temperatures of 48 degrees tomorrow, which would break the town's current record temperature of 47.2 degrees back in 1939.
Weatherzone's Angus Konta warns other records could be broken.
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"Some towns are currently forecast to reach 49°C, such as Walpeup, just over 100km south of Mildura," he said.
"This makes it possible that multiple records could fall, not just in Vic, but for SA and NSW."
Victoria's heat is intensifying the threat of bushfires that have been burning across the state all weekend, with fires in several areas of the state burning out of control.
Residents in parts of the Otway ranges, the Dargo area and near Walwa are being told to prepare for an evacuation as fire conditions continue to be severe.
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Brisbane will also see hot weather this week, experiencing a top of 36 degrees today, whilst Canberra will soar to 42 degrees on Wednesday.
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.
"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."
"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."
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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.
Ex-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 tropical low, but could still bring falls of up to 200mm in parts of WA.
Residents along the Kimberley coast should expect heavy rainfall and damaging winds over the long weekend, which is only expected to ease from Tuesday.
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Temperatures nudge close to 50 degrees as multiple states brace for record-breaking heat
