Winter warm spells are lasting longer, occurring more often and becoming more intense, a report by not-for-profit group the Climate Council found.
In addition to the warmth, the nation experienced its second driest June on record and the driest winter since 2002, the Hot & Dry: Australia's Weird Winter report found.
Ecologist Lesley Hughes said more than 260 heat and low rainfall records were set throughout the season.
"Without any meaningful action to tackle climate change, we will continue to see many more hot winters, just like this, as global temperatures rise," Ms Hughes said.
"We must take meaningful action to strongly reduce Australia's emissions from fossil fuels.
"The current situation in which the government continues to not only delay real action to reduce emissions, but is actively supporting further development of coal-fired power is simply nonsensical."
The unseasonable weather has led to an earlier start to the bushfire season in many parts of Australia, especially Victoria and other southern states, she said.
Professor Hughes urged the federal government to get on with tackling climate change.
"The solution remains the same - clean, efficient and affordable renewable energy and storage technology."
Australia's average winter temperatures have increased by about 1 degree since 1910, driven by climate change as a direct result of burning fossil fuels - coal, oil and gas, the council said.
The council was formed by Australia's biggest crowd-funding campaign after the Tony Abbott government abolished the Climate Commission in 2013.
The story 'Weird winter': Climate change behind Australia's record hot and dry weather first appeared on The Sydney Morning Herald.