Three capital cities are in for another day of sweltering temperatures as a heatwave continues to affect parts of the country.

Sydney, Adelaide and Canberra are all forecast to hit 40C on Thursday, following the hottest Australian day on record.

The average national temperature climbed to 40.9C on Tuesday eclipsing the record of 40.3C set in January 2013.

This record could be broken again with intense heat expected across most of Australia for Thursday and Friday.

South Australia will cop the brunt of Thursday’s heat, with the capital forecast to top out at 44C, and the western areas to be worse.

The southern-central town of Wudinna is forecast to hit 49C on Thursday, along with the Western Australian town of Forrest, in the state’s south east.

Bureau of Meteorology forecaster Simon Timcke said heat which has been building in the middle of the country is moving south, creating the extreme heat.

Advertisement
Advertisement

The heatwave will only continue to intensify, with southern and central Australia experiencing temperatures up to 16C above average by Friday.

Maximum temperature forecast, Thursday December 19:
Sydney 40
Melbourne 23
Brisbane 30
Adelaide 44
Perth 26
Hobart 23
Canberra 40
Darwin 35

© AAP 2019