Christmas Day dawns in Australia to cookie crumbs, empty milk glasses and screaming kids eager to see what Father Christmas brought them.

Early morning volunteering, church services and Christmas Eve hangovers all mark Christmas Day as Australians celebrate in their own way.

Religious leaders urge people in distress to embrace the time of hope, while Australia's leader wishes everyone a safe holiday period.

Prime Minister Anthony Albanese will help serve Christmas lunch to thousands of people who are homeless at the Exodus Foundation in Sydney's west.

He wished all Australians a safe and happy Christmas, noting many were doing it tough especially after floods damaged Queensland's far north.

"To them, I say, you are all in our thoughts. May better times be ahead," he said.

Opposition Leader Peter Dutton also wished Australians both a safe and merry Christmas.

"I wish all Australians a happy, relaxing and safe Christmas in the company of family and friends," Mr Dutton said.

"Whether we're Christians or not, at Christmas we give thanks for the things that we hold dear in life: our family, our friends, our faith and our great fortune to be an Australian," he said.

It will be far from beach weather on the east coast as Sydney, Melbourne, Canberra, Adelaide and Brisbane all brace for rainy days.

Both Sydney and Melbourne have a chance of thunderstorms.

The weather will be a lot warmer in the Top End and west, with Perth and Darwin set for temperatures in the mid-30s.

Tasmanians will mostly stay dry despite some cloud cover, with Hobart and Launceston expecting maximum temperatures in the mid-20s.

Millions of Australians are also preparing to splash some cash on Boxing Day sales.

The National Retail Association expects sales to hit $3 billion on Tuesday alone, with stores offering deep discounts after flat sales amid interest rate hikes and cost-of-living pressures on shoppers.

Australian Associated Press