Meteorologist Jackson Browne said there will be "quite a bit of severe weather occurring across different parts of Australia" on the national holiday.

"In the Tropical North, the monsoon returns to Darwin in time for Christmas. Rain returns to flood affected parts of eastern Australia and concerning extreme heatwave conditions for South West and Western Australia, including Perth. And this will carry the risk of some severe fire dangers for Christmas Day," he said.

Mr Browne said the weather will be "somewhat settled" in south-eastern Australia.

Sydney is forecast for a partly cloudy day with a minimum temperature of 21C and a maximum temperature of 31C.

Similarly, Canberra is forecast for partly cloudy day with a maximum of 30C although there is a medium (50%) chance of showers.

Meanwhile, Melbourne is forecast for a relatively cool day with a minimum of 16C and maximum of 21C.

Hobart is also set for a cool Christmas with a minimum of 15C, maximum of 21C and partly cloudy skies.

Mr Browne said a low pressure system will cause wet weather in parts of the NT and Queensland.

"In the tropical north, we can see a low embedded along the monsoon trough, dragging its way down towards the top end coast, with Darwin seeing a cool, wet Christmas Day," he said.

"Moisture sits to the east of an inland trough, so showers and storms for parts of Queensland. Cloudy one in Cairns. Rainy in Brisbane."

Mr Browne said weather will be "very settled across Adelaide and Alice Springs".

The South Australian capital is forecast for a minimum of 15C and maximum of 27C on Christmas Day while the Red Centre is forecast for a maximum of 35C.

"That high pressure ridge, which is bringing those settled conditions, is also creating quite a bit of heat along that Western Australian coast," Mr Browne said.

"So a very, very hot 42 degrees in Perth, with extreme heatwave conditions in the region."

Christmas Day forecasts:

Canberra: Min 15C, Max 30C. Partly cloudy with medium (50%) chance of showers.

Sydney: Min 21C, Max 30C. Partly cloudy with a 20% chance of a shower.

Melbourne: Min 16C, Max 21C. Becoming mostly sunny during the afternoon.

Brisbane: Min 22C, Max 28C. Cloudy with very high (90%) chance of showers.

Perth: Min 23C, Max 42C. Very hot and sunny.

Adelaide: Min 15C, Max 27C. Partly cloudy.

Hobart: Min 15C, Max 21C. Partly cloudy.

Darwin: Min 25, Max 31C. Showers. Possible storm. Most likely in the afternoon and evening.

Australia is currently going through a La Nina weather pattern. Want to learn more? Watch this video explainer: