· Perth hills bushfire destroys houses

Perth has sweltered through its hottest night on record, a portent of the extreme conditions that will pose a health risk across the southern states over the next week.

Temperatures in Perth peaked at more than 43C on Saturday, and dipped to a still-steamy low of 29.7 just after 3am on Sunday.

That beat the previous record of 29.3 in 1962. The mercury rose again to 39.7 in the city just after 9am.

The Bureau or Meteorology has forecast temperatures of at least 40 for five consecutive days in Adelaide, starting on Monday and peaking at 43 on Wednesday and Thursday. 

In Victoria, the bureau has forecast three days of more than 40 – Tuesday, Thursday and Friday – with no relief until Saturday. The temperatures for the first five days of the Australian Open, starting on Monday, are tipped to be 35, 41, 39, 41 and 40.

Other parts of the state are also set to sizzle, with five days in a row to hit above 40 in northern Victoria. In the towns of Echuca and Swan Hill the mercury is tipped to rise to 44 on Thursday and Friday.

“It’s the first burst of proper heat this summer,” said Bureau of Meteorology senior forecaster Terry Ryan.

But the heatwave is not likely to set records in Melbourne, which endured three consecutive days of at least 43 degrees in January 2009, the week before Victoria’s Black Saturday bushfires. “They were the hottest three days ever in Melbourne,” Mr Ryan said.

The longest hot spell recorded in Melbourne was in 1908, when the temperature hovered above 40 for five consecutive days.

Specialised firefighting choppers are on hand should conditions in Victoria deteriorate. Credit: AAP

Premier Denis Napthine urged Victorians to stay hydrated, look after their neighbours, particularly the elderly, and be aware of fire risks.

“We are in the height of our fire season,” he told reporters in Melbourne.

“I can assure Victorians all fire services are ready to deal with any emergency, but people need to be alert, people need to be conscious of the risk and people need to be prepared to make decisions to leave early and live.”

A change is expected to sweep through Melbourne late on Friday, with Saturday’s forecast of 26C to provide welcome relief.

The southern capitals will also experience sweltering nights. The minimum temperature predicted for Friday for both Melbourne and Adelaide is 28.

In South Australia, nurses will increase their checks on vulnerable people in the community as temperatures soar.

“Apart from the extreme coastal locations, you really could get a 45C-type maximum anywhere,” said senior forecaster Tom Boeck.

The State Emergency Service issued an extreme heat warning on Sunday and says hot weather conditions from Monday to Friday might be a risk to public safety.

Premier Jay Weatherill said people needed to revisit bushfire action plans and be prepared for an emergency.

“With several days forecast to be over 40 degrees, fire danger will be incredibly high, so it’s important people have plans in place to deal with an emergency,” he said.

Fire authorities will be on high alert, and police are expected to instigate Operation Nomad patrols, which check on known firebugs.