Data released this month showed average maximum temperatures in the winter months of June to August soared nearly 2C above average.
Climate change made the “exceptionally warm and dry” winter 60 times more likely, the Climate Council said in a report.
The group has linked the record hot winter to “worsening climate change”.
According to the report released on Tuesday, winter warm spells are also lasting longer, occurring more frequently and becoming more intense.
More than 260 heat and low rainfall records around the country were broken this winter, the report said.
It blamed climate change, and the burning of fossil fuels as having driven Australia’s average winter temperature up by about 1C since 1910, a figure reported by the CSIRO, the nation’s scientific research body last year.
“It is expected that the chance of warm winters like 2017 occurring will continue to increase as global temperatures rise,” the report added.
The Climate Council is an independent, non-profit organization that was set up in 2013 to continue the work of its government-funded predecessor, which was abolished by the Tony Abbott government.
In September, the Bureau of Meteorology released figures which showed Australia had undergone its hottest winter on record.
Average maximum temperatures from June to August were 1.9C above average, an increase of 0.3C above the 2009 record.
The Climate Council’s report also reiterated concerns raised by Australia’s fire authorities that the warm and dry winter had set the scene for a dangerous upcoming bushfire season. About one-third of Australia, including major capital cities on the east and south coasts, are facing an elevated bushfire risk for this summer.
Heat waves have increased in duration, frequency, and intensity across many regions in Australia, with large areas of the southeast suffering intense heat last summer.