An entire highway melts during Australia's heatwave as People warned to stay indoors as temperatures soar above 40C (Details, pics)

Australia's east coast is set to swelter over the weekend as Sydney and Melbourne are hit with a heatwave. Temperatures are expected to reach 40C as residents of both cities took to the beach to cool off on Friday.

A total fire ban was issued for Victoria on Saturday and a 10km stretch of the Hume Highway has begun to melt as a result of the heat.

Surging temperatures melted tar on the busy highway on Friday, causing a huge traffic jam as drivers dodged the sticky mess.

Residents have been urged to avoid the area and remain indoors over the weekend, as temperatures reach 40C.Melbourne is set to melt in 41C on Saturday, as thousands took to the beach on Friday in preparation for a hot and dry weekend. Relief will come on Sunday for Victoria, with temperatures expected to drop to 21 and bring cloudy conditions.

Sydney is also expected to swelter across the weekend, with tops of 38C on Saturday and 33C on Sunday.

South Australia and Canberra are also warned to brace for extreme heat, with a maximum temperature of 38C expected for the capital.

The Country Fire Service is bracing for 'catastrophic' fire weather in parts of South Australia on Saturday, with temperatures expected to reach up to 46 degrees.

Most of Tasmania has also been issued with a total fire ban, with temperatures expected to be in the mid-30s and northerly winds gusting up to 90 kilometres an hour, according to Weather zone.

Darwin is bracing for extreme conditions as well, with temperatures expected to hit mid-30s across the weekend and into the week.