Extreme weather is set to plague both the east and west coasts on Christmas Day.
West Australians are expected to swelter through their holiday lunches, with temperatures forecast to reach the high 30s-low 40s for a large part of the state.
The heat wave stretches from Karratha, in the Pilbara region, down to areas south of Perth.
The hot conditions, combined with dry, gusty thunderstorms, have fuelled fire risk and extreme fire danger is forecast for the midwest coast to the capes.
"Fairly concerning conditions for our firefighters," Bureau of Meteorology senior meteorologist Miriam Bradbury told ABC TV on Thursday.
On the other side of the country, rain is set to batter Queensland and the Northern Territory, while further south residents will shiver through their celebrations.
Severe thunderstorms have been forecast for parts of Queensland's Wide Bay area near Monto, while regions in the state's northwest and the adjacent territory have been warned to watch for flooding as a monsoon trough lingers.
Tropical Cyclone Grant is set to pass by the Cocos (Keeling) Islands - a remote Australian territory about 2700km northwest of Perth - bringing rain and the risk of damaging wind gusts.
Maximum temperatures are expected to reach just 15C in Hobart, while Melbourne has a forecast high of 17C - which would be the city's coldest Christmas in nearly two decades.
The mercury is predicted to hit the low-mid 20s in Sydney and Adelaide, while Brisbane will be warmer at 34C.
The usually joyous time of year has already been marred by the massacre of 15 people when gunmen targeted a Jewish celebration at Australia's most iconic beach.
But Catholic Archbishop of Sydney Anthony Fisher said light would shine through the darkness following the anti-Semitic terrorist attack at Bondi Beach.
Two Islamic State-inspired gunmen killed 15 people on December 14, which marked the start of Hanukkah, the Jewish festival of light.
"In a season when both Jews and Christians celebrate light and hope, we have been confronted with profound evil," Archbishop Fisher said.
"As many in our city grieve this Christmas, let us declare boldly: the light shines in the darkness and the darkness has not overcome it."
The 2025 Christmas message from the president of the Uniting Church in Australia, Charissa Suli, also proclaimed light would prevail in the face of fires, floods and conflicts that marked 2025.
In her Christmas message, Reverend Suli proclaimed the light of Jesus would prevail and that was why "Christmas still matters".
"That light doesn't ignore the darkness, it transforms it and it calls us to compassion, generosity and justice," she said.
Bishop of Parramatta Vincent Long called for Australians to act and help make a difference in the face of suffering and pain.
"Daily, our hearts continue to break when we see the violence, especially to children, in places like Gaza, Ukraine and Myanmar - we cannot just watch all this suffering in front of our eyes passively," he said.
"My prayer, therefore, is that each of you will feel God's closeness and become instruments of peace in the New Year ahead."
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