Data released this month showed average maximum temperatures in the winter months of June to August were 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".
The Climate Council is an independent, non-profit organisation that was set up in 2013 to continue the work of its government-funded predecessor, which was abolished by the Tony Abbott government.
