An extreme heatwave occurred in south-eastern Australia, January 1939. It was long lasting with very high temperatures. On 9 January the temperature at Kyancutta (South Australia) reached 49.3 °C, the highest temperature recorded in South Australia at that time.

Many temperature records were made during this heatwave, some of which have held until the recent 2009 heatwave; Adelaide, 46.1 °C, on 12 January, Melbourne, 45.6°C on 13 January, Sydney, 45.3°C on 14 January with Manly and Richmond both reaching over 47 °C. In northern New South Wales some places reached 48 °C on 15 January. Menindee in western New South Wales reached 49.7 °C.

High temperatures were experienced inland in 1939; at Mildura the temperature exceeded 37.8 °C on each of the first 14 days of January, and at the peak of the heatwave, averaged 45.6°C from 7-14 January. It is estimated that more than 400 deaths in Victoria were caused by excessive heat.

The strong northerly winds in 1939 over this period followed a very dry six months providing the right conditions for extreme bushfire, see the related entry for the 13 January 1939, Black Friday bushfire.