The rise in the number of extremely hot days is underlined in a new report that finds there were more in 2013 than in the entire 1910-40 period combined.
The State of the Climate report by the Bureau of Meteorology and CSIRO finds Australia is being hit by more extreme heat and high-fire danger, and southern regions are drying out - trends that may accelerate as the planet heats up.
The biennial survey found mean temperatures nationwide had risen 0.9 degrees since 1910 and will be another 0.6-1.5 degrees warmer by 2030, compared with the 1980-99 average.
By 2050, if greenhouse gas emissions continue to grow at the pace of the past decade, temperatures will rise between 2.2 and 5 degrees above the 1980-99 average, the agencies said.
Karl Braganza, head of climate monitoring at the bureau, said the rising tally of very hot days in the top 1 per cent of mean temperatures was significant.
Last year, Australia's hottest, recorded 28 such days - more than for the entire 1900-40 period. ''We're more frequently seeing that heat widespread across the whole continent. It's not just dominated by one region,'' Dr Braganza said.
Penny Whetton, a climate projection expert at CSIRO, said: ''We expect there to be a continuation of [the] warming and probably an acceleration … in the decades to come.''
Since 2001, record warm night-time temperatures have been five times as likely as cool ones, while there have been three times the number of record day-time maximums compared with cold ones.
Half of the extreme heat days over the past century have been registered in the past 20 years.
''That does pose a risk for fire danger and indeed the work we've done has indicated an increase in the fire weather conditions in the future in southern Australia,'' Dr Whetton said.
The report was released after the Abbott government's bid to axe the Climate Change Authority was blocked in the Senate on Monday, ensuring the body that offers advice on climate policy and targets would survive until at least July 1. Environment Minister Greg Hunt last week said the authority was not needed because the bureau and CSIRO provided ''comprehensive and independent advice'' on climate change.
The State of the Climate report makes for grim reading for farmers reliant on cool season rains. Since the mid-1990s, rainfall in the south-east has fallen 25 per cent in April and May and 15 per cent in the late-autumn, early-winter period.
The findings come less than a week after the Abbott government unveiled a $320 million drought package to aid farms mostly in Queensland and northern NSW.
Note: An earlier version of this article incorrectly stated the number of hot days in 2013 exceeded the total of the first four decades of the 20th century when in fact the number exceeded the tally for the 1910-40 period.