Sky News Weather meteorologist Rob Sharpe said it's looking to be a very hot week ahead, with some areas seeing their hottest run of December days in years.
"Many people will remember we had prolonged very warm weather across the south-east of the nation towards the end of November," he said.
"This was mainly due to a blocking high that set up in the southern Tasman Sea.
"The high drew heat from the north of the nation into the south and south-east, blocking most cool changes from affecting the region and leading to an extended period of spring heat."
Sharpe said Australia was now expecting a similar situation, but this time the high should sit a little further north in the Tasman Sea.
"This means that the focus of the prolonged heat will be further north-east than what we saw last month," he said.
"Heatwave conditions are likely to affect large parts of New South Wales and south-western Queensland."
Sharpe said Canberra is expecting to see seven consecutive days above 30 degrees, the first time this has occurred in 54 years.
The inland NSW town of Dubbo is on track for a heatwave and is expected to have six days at or above 37C.
"Dubbo's December average is merely 31 degrees," he said.
Western Sydney is also expecting a hot run of days, with the temperature tipped to hit 41C on Thursday.
"Richmond is set to exceed 35 degrees each day from Wednesday to Saturday, its hottest December spell in at least 12 years," Sharpe said.
"Sydney itself will see seven straight days above 27, with unseasonably humid nights above 20 degrees from Wednesday night into the start of next week."
South Australians can expect some relief from the hot conditions with the capital set to reach 36C today and 38C tomorrow.
"The heat will leave abruptly as a cool change arrives late on Wednesday, dropping the temperature by about 10 degrees in an hour near dinner time," he said.
"On Wednesday, Melbourne will see its hottest day since last summer, likely reaching 36 degrees."
In NSW, around half of the state has already begun experiencing a low-intensity heatwave that will strengthen as the week goes on, according to the Bureau of Meteorology.
Here's what the weather will look like across the country this week.
SYDNEY
The city can expect a top of 27C today, 30C tomorrow, 33C on Thursday.
Temperatures will be even hotter in the west, which can expect highs of 34C, 38C and 41C.
MELBOURNE
The city will hit temperatures of 26C today, 36C tomorrow and 27C with the chance of showers on Thursday.
The town of Yarra Glen, 40km north east of Melbourne, is set to reach temperatures of 30C, 36C and 28C.
HOBART
The Tasmanian capital will hit a high of 25C today, 31C tomorrow before a cool change of 23C on Thursday.
CANBERRA
The Australian capital will hit a high of 31C today, 34C tomorrow and 34C on Thursday.
DARWIN
The city will reach 35C today, 34C tomorrow and 34C on Thursday with showers and possible storms expected.
PERTH
After a stinking hot start to the week yesterday, Perth is set to cool down a little with the mercury hitting 29C today, 27C tomorrow and 29C on Thursday.
ADELAIDE
The city will hit a top of 36C today, and 38C tomorrow before a cool change brings the temperature back down to 24C by Thursday.
BRISBANE
The capital of the Sunshine State will hit a high of 29C today, 30C tomorrow and 31C on Thursday.
