The Australian Institute (TAI) analysed Bureau of Meteorology (BoM) data to track changes in daily temperatures that mark the beginning of each season.

It found in the past two decades, summer temperatures were experienced for 31 days more than the mid-twentieth century benchmark.

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TAI climate and energy director Richie Merzian said temperatures consistent with a regular three-month summer in the 1950s now spanned from early-to-mid November, all the way to mid-March.

"Our findings are not a projection of what we may see in the future, it's happening right now," Mr Merzian said.

"Summers have grown longer even in recent years, with the last five years facing summers twice as long as their winters.

"Place such as Port Macquarie in NSW, which suffered devastating fires early in the fire season, are now experiencing seven more weeks of summer compared with the 1950s and '60s."

Mr Merzian said the extended summers would have a significant impact on agriculture, damaging crops and exhausting livestock.

It'll also affect the nation's tourism, construction and mining sectors, and increase the impact of bushfires.

"As the length of the bushfire summer season extends, the window to enforce bushfire management strategies, typically in winter, shrinks," Mr Merzian said.

The report found winter temperatures were experienced for 23 days less over a three-week period.

Under questioning during this week's Senate estimate hearings, Bureau of Meteorology director Andrew Johnson said the "warming and drying trend" was "inarguable".

"Based on current trajectories of global emissions into the atmosphere, that warming and drying trend is likely to continue," Dr Johnson said

"2019 was a very difficult year. It nationally averaged the hottest and driest that we've seen since records have been kept at the beginning of the 20^th century."

Dr Johnson was careful when asked how much of a role climate change played in the drought and recently bushfires, but said it was certainly a contributing factor in both events.

Mr Merzian said it was in Australia's national and economic interest to put in place a strong emissions reduction policy.

"The Australian government's current policies only serve to further fuel the climate crisis," he said.