Record-breaking heat has hit southeastern Australia over the past few days leading to widespread fire bans as temperatures passed 40 degrees Celsius.

Canberra had its hottest day of the summer so far with a high of 40C on Saturday afternoon. There was some relief for the nation's capital by dawn as temperatures fell back to 15C.

It was even hotter in Sydney were the western suburb of Penrith recorded a high of 47.3C. This was the city's hottest day in 79 years, falling just short of the all-time record of 47.8 in 1939.

Temperatures are gradually expected to ease over the next few days. Showers are expected on Monday and Tuesday before the winds swing round to the southeast. Highs should then fall back nearer the seasonal average of around 25 degrees.

Bushfires threaten homes

Total fire bans and severe fire danger warnings have been issued by the New South Wales Rural Fire Service for the Hunter and Greater Sydney. These bans will remain in force into the start of the working week.

Meanwhile, bushfires have broken out in parts of Victoria. Residents of Carrum Downs on the southern outskirts of Melbourne were evacuated from their homes on Saturday as a bushfire edged closer, local media reported.

Firefighters battled extreme heat and high winds, with a number of outbuildings and at least one home set alight as flames spread from nearby bushland.

Two water-bombing helicopters were brought in to help contain the blaze. Residents who were evacuated were told to congregate at the local shopping centre.

About 50 fires have been reported around the state. Temperatures peaked at 42C on Saturday, before cooler air pegged the heat back to a more comfortable 21 degrees on Sunday.