The red-hot start to October barely let up, setting Australia up for its most abnormally warm month in records going back to 1910, the Bureau of Meteorology said.

The arrival of summer-like conditions several months early has combined with on-going dry conditions in many southern parts of the country to create dangerous fire conditions, authorities say.

Nationally, maximum temperatures were 3.44 degrees above average for October, eclipsing the previous record deviation of 3.41 degrees set in September 2013, the bureau said its monthly climate report.

The unusual heat was even more notable for mean temperatures, which take the average of days and nights. Last month was 2.89 degrees warmer than the long-term average, beating the previous record mean anomaly of 2.75 degrees, also set in September 2013. Minimum temperatures, too, set a new high for the month.