Hervey Bay in south-east Queensland has recorded its coldest April morning in more than 14 years.
The weather bureau says it got to just seven degrees Celsius on Sunday morning.
Forecaster Brett Harrison says despite the cold snap it should warm up by the end of the week.
"This morning it's been a touch warmer," he said.
"We do expect the minimums to be even warmer again tomorrow so returning to average for this time of the year."
© ABC 2013
15:51 EDT Forecasts still suggest Christmas Day in Australia will be typically hot, humid and thundery in the north, windy in the south, wet in the southeast and dry and warm on the west coast.