 The highest summer maximums in the Pilbara and Gascoyne average at around 41 °C (in some years daily maximums consecutively exceed 40 °C for several weeks at a time).The most powerful heatwave in the history of south-eastern Australia occurred in January 1939.Adelaide (46.1 °C on the 12th), Melbourne (45.6 °C on the 13th) and Sydney (45.3 °C on the 14th) all had record-high temperatures during this period, as did many other central district areas in New South Wales, Victoria and South Australia.