Australia's first major heatwave of the warming season has broken temperature records across the nation, more than a month before the official start to summer.

On Saturday, the country set its warmest October day in records going back to 1910, with average maximums across the nation reaching 36.39 degrees, according to the Bureau of Meteorology.

Good for sun lovers: Record October warmth for Australia. Credit:James Alcock

The previous record for October was set on the 31st of the month in 1988, at 36.31 degrees.

Sunday's heat was almost as fierce as Saturday's, according to preliminary figures.