Melbourne is set for a cool and windy Christmas, while rain is forecast in Sydney and Perth is set for a scorcher.

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.

Melbourne could have its coldest Christmas day since 2006, when it only reached 14.5C. The city can expect a cloudy day with medium chance of showers, rainfall totals across the city should be less than 5mm, with less than 1-2mm more likely.

There would be heatwave conditions and extreme fire danger in parts of WA over Christmas, particularly around the south-west, said Natural Hazards Research Australia’s chief executive, Andrew Gissing.

“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.

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“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 (27C) and Adelaide (25C) were the only capitals expecting a fine and relatively mild Christmas Day, while Sydney, Melbourne, Brisbane, and Hobart could expect showers, according to the Bureau of Meteorology. Darwin could get a 50mm tropical downpour.

On Christmas Day, Sydney can expect a shower or two and a top of 23C, and Brisbane is predicted to be a balmy 34C.

Perth will have a scorcher, with 41C forecast before a milder 27C on Boxing Day.

Hobart will experience the coolest temperatures of all the capital cities on Christmas Day, with a top of 15C, while Darwin is expected to hit 31C.

Australia has been experiencing a “reasonably active” bushfire season amid hot weather, said Gissing.

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

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

“And 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.”