Australia will post one of its warmest autumns on record and faces a milder and drier than usual winter ahead as the country endures its hottest start to any year.

The Bureau of Meteorology said the March-May period will be among Australia's warmest five autumns in records that go back to 1910 even taking into account a wintry blast to end the season. For NSW, the ranking is likely among the top five warmest and for Victoria, the top 10.

A Kings Cross resident feeds a gang of cockatoos gathered outside his kitchen in the late autumn afternoon sunlight. Credit:Peter Rae

Blair Trewin, senior climatologist for the bureau, said "we're still tracking the warmest on record nationally" for the first five months of the year. This is a record hot start to any year, including Sydney and the eastern two-thirds of NSW and Victoria.

Recent autumns have been exceptionally warm, especially in 2016 when the season was about 0.6-0.7 degrees warmer than the season now drawing to a close, Dr Trewin said.