A huge swathe of Australia is forecast to roast in mid-40 degree heat on Friday, with more records likely to be broken at the tail-end of a heatwave that set a slew of national highs last month.
The mercury is tipped to reach at least 45 degrees over a region stretching from northern Western Australia into Victoria and the NSW Riverina.
By 1pm, Melbourne had touched 39.4 degrees on the way to a predicted top of 42 degrees. Walpeup in the state's north had reached 45 degrees while across the border in South Australia, Renmark was on 46.2 degrees.
Sydney continued to be spared the worst of the heat with a maximum of 29 forecast although the western suburbs are likely to nudge towards the 40-degree mark on Friday. Deniliquin in the Riverina was the hottest in NSW at 44.1 degrees.
"It's definitely been a prolonged spell of heat," Graeme Brittain, a meteorologist for Weatherzone, said.
Twin high pressure systems have all but set up camp over the Tasman and the Great Australian Bight, leaving the heat to pool in a broad trough that has oscillated marginally north and south for more than a week.
Early on in the event, a slew of Australian records were set, such as a record 40.21 degrees average maximum for December on the 27th of the month.
That mark was also the second hottest day for any month of the year, the Bureau of Meteorology said.
The following overnight temperatures also brought Australia's highest average minimum December temperature of 24.16 degrees.
December 29's minimum was almost as warm, coming in at an average of 23.66 degrees – the second highest minimums on record for any December, the bureau said.
Melbourne is due to get some relief by Friday afternoon, with Saturday's maximum tipped to reach a relatively chilly 21 degrees.
Coastal NSW and Sydney will heat up on Saturday with temperatures in the mid-to-high-30s forecast.
Relief from the heat over south-eastern Australia will be temporary, though, with another spike in temperatures likely by next weekend, Weatherzone's Mr Brittain said.
Second-hottest year for daytime readings
The year-end boost to temperatures meant Australia posted its hottest December on record.
Average readings were more than two degrees above the 1961-90 baseline for both maximum and mean temperatures, bureau data shows.
That hot end to 2018 also suggests last year was Australia's second-hottest year on record for maximum temperatures, trailing only 2013.
Mean temperatures for 2018 were the third-warmest on record, with the bureau due to release its year-end report in coming days.
Peter Hannam is Environment Editor at The Sydney Morning Herald. He covers broad environmental issues ranging from climate change to renewable energy for Fairfax Media.