The temperature in Sydney hit an almost 80-year high of 47.3 degrees Celsius (117 Fahrenheit) on Sunday — a sharp contrast to the bitter cold that has gripped much of the US.

The temperature was just shy of the city's all-time high of 47.8 C (118F), set in 1939.

New South Wales Police Deputy Commissioner Catherine Burn said the state's heat wave plan had been activated to respond to "severe to extreme heat conditions."

Thousands were left without power, and total fire bans were put in place as officials warned of a severe danger.

Residents were urged to drink extra water and limit their time outdoors because of air pollution resulting from the hot weather.