"We're likely to see a broad part of the country experiencing temperatures in excess of 45 degrees from Wednesday onwards," Ms Eadie said.
Areas likely to swelter include much of South Australia, the far south eastern corner of Western Australia, north and western Victoria, and the south and central parts of NSW.
"We'll see temperatures about 12 to 16 degrees above average for this time of year," she said.
"We'll see exceptional heat and there is the potential that we could see some records broken."
It's possible the record for Australia's hottest day could fall.
The South Australian outback town of Oodnadatta, located about 873 kilometres north of Adelaide and about five hours drive from opal mining town Coober Pedy, currently holds the record for the highest ever recorded temperature of 50.7C, which was set in January 1960.
The record for the highest average temperature for Australia as a whole may also be exceeded. The current record stands at 40.3 degrees and this was set in January 2013.
Sky News Weather channel meteorologists said Perth had been sweltering through a heatwave that could send the city above 40 degrees on three consecutive days in December for the first time in more than 120 years of data records.
This heat will be pushed east when a cool change reaches the west coast late on Sunday, and could drive up temperatures in some inland South Australian towns above 50 degrees.
Other parts of South Australia, northern Victoria and inland New South Wales are also forecast to reach the mid to high 40s.
"In the past, Australia has only recorded temperatures above 50 degrees on three occasions, the most recent being Mardie in Western Australia's Pilbara region in 1998, and Oodnadatta in South Australia, which reached 50 degrees twice in 1960 and still holds the record of 50.7C set in January of that year," Sky News Weather meteorologist Rob Sharpe said.
"We have the perfect set-up for record temperatures. If we don't break 50 degrees next week, it's quite likely at least one town in Australia will before the end of January."
Darwin has already broken its December record for the number of days above 35 degrees and official data shows 2019 is on track to be one of the hottest and driest years on record in Australia.
The extreme heat will also bring a widespread fire threat across southeast Australia. More than 700 homes have been destroyed by bushfires in New South Wales alone this season.
Next week, it is likely more homes will be lost as temperatures soar into the 40s over inland NSW and northern Victoria.
