Emergency workers and defence personnel have received well wishes from both the prime minister and Labor leader Bill Shorten in their official Christmas messages.
Malcolm Turnbull's expected to visit the homeless shelter Wayside Chapel in Sydney's Kings Cross today and the PM says it's a reminder to reach out and give a hug to vulnerable people on Christmas Day.
Mr Shorten's also used his message to remind Australians to spare a thought for people who are doing it tough, thanking those who'll be providing them a little bit of Christmas cheer in hard times.
About 2,300 Australian soldiers, sailors and aircrew are deployed around the world this Christmas.
Their duty sees them involved in ongoing operations in the Middle East, Africa and even in Australia's northern waters.
Mr Turnbull says members of the defence force overseas are close in the thoughts and hearts of Australians this Christmas.
In his message to ADF personnel, he's paid tribute to those who serve their country and who've died in that service.
The PM says in 2016 the ADF has delivered a compassionate, humanitarian response to tropical cyclone Winston in Fiji, continued maritime security operations in the Middle East and continued to assist in UN operations in South Sudan.
Mr Shorten also payed tribute to the troops overseas and their loving families back home who also serve, as well as emergency services personnel.
"We think of all those Australians working this holiday season to make our Christmas run smoothly - modest heroes who get up before the sun rises or work through the night," he says.
"Hard-working people, relying on penalty rates to provide for their families - something I'll always fight for."
Members of Australia's Defense force in the Middle East have posted their Christmas messages via social media.
"I miss you guys," Lieutenant James Ponella, an officer deployed in Iraq, said to his family via a video message.
"But I'm proud to be here doing what Aussies do best — helping out our mates."
Shorten's Christmas penalty rates pledge
The Shortens are remembering the "modest heroes" who will be busy working this Christmas and relying on penalty rates while others relax.
The Labor leader has again filmed his annual Christmas message with wife Chloe, with the pair reflecting on those who will be serving others through the break.
Christmas is also a time to spare a thought for those doing it tough - the homeless, those battling loneliness and women and children in refuges, they say.
"We're so lucky that many Australians will roll up their sleeves to provide hot meals, secure accommodation and a little bit of Christmas cheer in hard times."
Ms Shorten urges Australians to be careful on the roads and stay safe around the water.
"We hope all of you have a relaxing break, with the people that you love," her husband says.
"From our family to yours, Merry Christmas."
Southeast Australia to swelter
Parts of the country's southeast will swelter on Christmas Day, with humidity in the region expected to approach or exceed December records.
A severe heatwave is affecting parts of NSW, Victoria, South Australia and Tasmania, with the average Christmas night temperatures for Tasmania and Victoria forecast to be the warmest on record.
Adelaide is expected to experience its warmest Christmas Day since 1945, with a 40C maximum.
Melbourne's forecast 35C maximum would be the hottest since 1998.
Bureau of Meteorology senior meteorologist Jenny Sturrock says a trough over Western Australia has contributed to high humidity levels in the country's southeast, with "noticeably muggy" conditions unusual for the time of year.
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Ex-tropical cyclone Yvette is expected to cross WA's Kimberley Coast on Christmas Day as a low pressure system before dying off around Boxing Day.
"At this stage (it's) unlikely to develop into a cyclone again," Ms Sturrock said
"But it still could get quite strong winds.... and also some heavy rainfall adding to the already increased falls that region has seen."
Hobart will experience a max of 26C, which is more than 5C above average.
Canberra (31C max) and Brisbane (28C max) may experience showers, while a possible storm is forecast in Darwin where the temperature is expected to reach 33C.
Sydney is expected to reach a maximum of 27C.
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