Forecast rain is dampening the risk of bushfires on Christmas Day for most capital cities, but parts of the nation will be on heatwave alert.

Australia had already experienced a “reasonably active” bushfire season, Natural Hazards Research Australia chief executive Andrew Gissing said.

“In NSW we had about 16 homes lost recently, a similar number at Dolphin Sands in Tasmania and there’s been a few lost in WA as well, and tragically, we’ve lost firefighters as well,” he said.

There will be heatwave conditions and extreme fire danger in parts of Western Australia over Christmas, particularly in the south-west, he said.

“WA folks are facing extreme heat … the strength of the winds and the relatively low humidity is taken into account when calculating those fire danger ratings,” Gissing said.

“WA has also been experiencing this longer-term drying trend, which has been escalating … and when you have bushfire and extreme heat, you’ve also got the associated health risks of the bushfire smoke.”

Canberra (27 degrees) and Adelaide (25 degrees) are the only capitals expecting a fine and relatively mild Christmas Day, while Sydney, Melbourne, Brisbane, and Hobart are expecting showers, and Darwin could get a 50-millimetre tropical downpour.

Sydney can expect a top of 23 degrees, Melbourne a chilly and windy 17 and Brisbane a balmy 34.

Perth will have a scorcher on Christmas Day with 41 degrees forecast ahead of a milder 27 degrees on Boxing Day.

“Other than bushfires, you’ve also got widespread heavy rainfall across northern Australia, which will lead to potential flooding,” Gissing said.

“You’ve also got this category two cyclone that’s firmed up in the Indian Ocean, which might impact the Cocos Islands on Christmas Eve and Christmas Day as well.”

Elsewhere, forecaster Weatherzone warns that some models predict a dangerous wet spell for some parts of Queensland in the days after Christmas – “enough rain to cause flooding between Christmas and New Year’s Eve”.

“At this stage, a coastal trough and an inland low pressure system are expected to interact with copious tropical moisture to cause widespread rain and storms over central and northern Queensland from this Friday, December 26, through to at least early next week,” Weatherzone said.

The areas currently most likely to see heavy rain and flooding from this system are central and northern Queensland, extending from the central coast up to the Gulf of Carpentaria and across the border into the Northern Territory.”

-with AAP