Australia experienced its third-warmest year on record in 2017, according to the nation's Bureau of Meteorology.
The national mean temperature of 22.75C was almost 1C higher than a 1961-1990 baseline, its annual report revealed.
Only 2005 and 2013 were warmer, based on records kept for about a century.
In November, the World Meteorological Organization projected that 2017 was "very likely" to be among the hottest years ever globally.
The majority of Australia saw above-average heat, with maximum temperatures the second-warmest on record, the bureau said.
"Despite the lack of an El Niño - which is normally associated with our hottest years - 2017 was still characterised by very warm temperatures," said Dr Karl Braganza, head of climate monitoring.
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Summer heat described as "exceptional" had resulted in several land-based records being set in New South Wales and Queensland.
In its annual report released on Wednesday , the bureau said seven of Australia's 10 warmest years had occurred since 2005. Only one year, 2011, had cooler than average temperatures.
It also reiterated that the Great Barrier Reef had suffered consecutive years of mass bleaching due to elevated ocean temperatures.
Climate change caused by human activity had contributed to the annual mean temperature increasing by about 1.1C since 1910, the report said.
On Sunday, Sydney experienced its hottest day in 79 years when temperatures hit 47.3C. A previous study has warned Australia's biggest cities could face 50C temperatures by 2040.