• First heatwave definition released by Bureau

The heat is on across large parts of southern Australia, with Adelaide and Melbourne just days days into a week-long heatwave, while bushfire-ravaged parts of Western Australia brace for another bout of extreme heat late in the week.

Temperatures stayed high over Tuesday night, with Melbourne only dipping below 30 degrees after 5am as Adelaide is set for another 45 degree day, with 46 forecast for Thursday. Just before 8am AEDT Melbourne was 31.2 degrees and Adelaide 28.5.

On Tuesday afternoon, the Adelaide temperature had topped 45 degrees, three degrees above the forecast. Melbourne hit 42 degrees, temperatures in Canberra surpassed 37 degrees and parts of south east Tasmania edged toward 40 degrees.

But anyone hoping for relief will have to wait for the weekend with the mercury expected to remain uncomfortably high for the rest of the working week.

Peter Ryan, acting premier of Victoria, said local firefighters faced their most challenging conditions since the catastrophic events of Black Saturday in 2009.

A total fire ban remains in place in Victoria, where firefighters worked through the night battling several blazes.

David Gibbs from the Country Fire Authority (CFA) says fire destroyed a cafe at the Heronswood Gardens at Dromana on the Mornington Peninsula.

“Heronswood itself has not burnt down, the cafe that is on the property has burnt down, and there is some damage to the building itself,” he said.

Fire crews have also been working overnight to contain a bushfire at Kangaroo Ground, north-east of Melbourne.

They brought the fire at the Koos Road Reserve and north of Dawson Road under control last night but are still working on containment.

Finding ways to beat the heat in Adelaide. Photo: Getty

“These next four days promise to be amongst the most significant that we have faced in Victoria since Black Saturday,” he told reporters at the State Control Centre in Melbourne.

Mr Ryan said Victoria, one of the most fire-prone locations on earth, was vastly better prepared for fire than it was five years ago.

“We are alive to the fact that we face these challenges over the course of these coming four days, including today, but on the other hand we are well prepared. We are ready to go,” Mr Ryan said.

In Victoria, the hottest temperatures were recorded in Charlton (46.3C), Swan Hill (45.2C) and Walpeup (45.2C).

South Australia sizzles

The city had its fourth hottest day on record yesterday,  reaching 45.1C, and the temperature is expected to hit 45C again today.

Adelaide’s continuing #heatwave brings a stunning sunrise ahead of a 45 deg day. @7NewsAdelaide @sunriseon7 pic.twitter.com/lLOOdo66Ik

— TIM MORRIS (@Tim_Morris14) January 14, 2014

It could get even hotter over the next couple of days with 46C forecast on Thursday, before 40 on Friday. The city’s record maximum is 46.1, recorded in January 1939.

More than 300 CFA crews have fought scores of fires, many started by lightning strikes.

A woman was taken to hospital after she was burnt while trying to save her home from fire at Rockleigh, south-east of Adelaide.

The CFS is also battling fires on Lower Eyre Peninsula, and in the Barossa and Clare Valleys.

South Australian Premier Jay Weatherill has urged all people to take care of those most vulnerable to the heat, including elderly relatives, friends and neighbours.

He says people without air-conditioning at home should consider heading to cooler public facilities such as cinemas, shopping centres and libraries.

For the remainder of the week, people in Adelaide face forecast temperatures of 45 for Wednesday and Thursday, 40 for Friday and a more-comfortable 28 for Saturday.

“Almost everywhere in SA is experiencing very hot temperatures in the low to mid-40s and some locations today experienced their hottest day ever,” the Bureau of Meteorology’s Paul Lainio said.

After braving a heatwave (defined as three or more days of unusually high temperatures) in 2009, other parts of South Australia may need to brace themselves again this week, with the heatwave warning also stretching across much of the state’s south-west.

Several other South Australian towns were even hotter than Adelaide on Tuesday, with the fiercest temperatures across the state recorded in Pallamana (46.3C), Port Augusta (46.2C) and Lameroo (46.2C).

Canberra warnings

Emergency services are urging ACT residents to be wary, as Canberra begins what is expected to be the hottest week this summer.

Temperatures climbed towards 40 degrees in the capital, well above the January average of 28 degrees.

Canberra is expected to hit 39 degrees on Wednesday and Thursday, and 38 degrees on Friday.

The ACT Ambulance Service is reminding residents not to leave children and pets in cars and for the elderly to keep out of the heat.

Service chief David Foot says Canberrans should keep well hydrated and cool, especially during the hottest part of the day.

“The clear message for everyone is we are going to run into the hot weather, be sensible, look after yourselves [and] look after your neighbours as well,” he said.

Low winds are expected to keep the edge off the bushfire danger, but fire authorities are warning Canberrans to remain vigilant.

— With Jackson Stiles