Temperatures will exceed 40°C across a 4000 km stretch of Australia later this week as a massive pool of hot air spreads across the country.

A hot air mass that is building over WA at the start of this week will begin to spread over central and southern Australia from Wednesday, before spilling into eastern Australia from Thursday into the weekend.

Image: Visible satellite image showing clear skies over much of Australia on Tuesday, which is allowing heat to build up. Source: Weatherzone.

As this heat spreads towards the east, it will intensify over the cloud-free Australian outback and create huge region of sweltering temperatures that will extend from the northwest of WA all the way to Australia’s east coast.

The animation below shows the hot air spreading over Australia between now and the weekend.

Image: Forecast daily maximum temperatures between Tuesday and Sunday this week. Source: Weatherzone.

Temperatures are expected to reach their peak intensity and spatial coverage on Saturday. Some areas in central Australia could reach around 46 to 48°C on Saturday afternoon, with temperatures also forecast to exceed 40°C as far west as about Onslow and Karratha in WA and as far east as part of Sydney and the Mid North Coast in NSW, an area stretching almost 4000 km across five states and territories.

This week’s impending hot weather will cause temperatures to climb abruptly in southeastern Australia, following an abnormally cold start to summer that saw snow falling in the Alps on the first day of the season.

Melbourne only reached 16.1°C on Monday and is forecast to reach 33°C by Thursday. Sydney only reached the low twenties on Tuesday and is predicted to hit 37°C on Saturday.

At this stage, Australia's December maximum temperature record of 49.9°C at Nullarbor, SA in 2019 is not expected to be challenged by this week’s heat.