25/12/2016 10:33 AM AEDT | Updated 25/12/2016 6:28 PM AEDT

South Australian Capital Swelters Through Hottest Christmas Since 1945

Adelaide claimed hottest Christmas city in the world.

David Gray / Reuters
Many parts of Australia are set to swelter through a very hot Christmas Day.

Large swathes of Australia are set to swelter through Christmas Day, with the mercury soaring in many parts of the country, especially the nation's southeast.

The hottest capital city has been Adelaide, reaching 40 degrees at 2:29pm, according to the Bureau of Meteorology (BoM). It's the city's hottest Christmas in 70 years.

Melbourne, Perth, Darwin and Canberra all reached 30C and beyond, perfect for BBQ weather if you're wearing a wide brim hat.

BoM reported less sizzling conditions of Sydney and Brisbane, which is set to reach a maximum of 29C.

Hobart has been the coolest of the Australia's capitals, at a pleasant 24C.

Judging from social media, the extra hot conditions don't seem to be taking the edge off Christmas cheer.

Merry Christmas Brisbane! May your drinks be cold, your shirts bold and your zinc applied in excess. #HappyHolidays

A photo posted by The Gabba (@thegabbabrisbane) on

Merry christmas mates!! 🎉🇦🇺 #36 #degrees #australia #stkilda

A photo posted by Its A Way Of Living 💫 (@jimmyslifestyle) on

A trough over Western Australia will contribute to the high humidity levels in Australia's southeast, BoM senior meteorologist Jenny Sturrock told Nine.

Sturrock expected there to be "noticeably muggy" conditions over large parts of the nation's southeast.

In Victoria, where scorching conditions are predicted for many parts, authorities warned holiday makers to be prepared for fire danger.

"So this weekend is one of those drying periods that will see what parts of the state that aren't already dry, to dry out and set us up for January and February," Emergency Management Commissioner Craig Lapsley told the ABC.

"But there is already much of the state that is already ready to burn.

"If you see a fire report it. Don't drive towards smoke, drive away from smoke."