Residents in the path of a Victorian bushfire have been told to evacuate, as the mercury climbs to “unheard of” new state records on Tuesday afternoon.

An out-of-control blaze in the Otways jumped containment lines and was  threatening nearby communities, with at least three homes lost.

Temperatures soared across Victoria and South Australia on Tuesday, with extreme peaks anticipated in the afternoon.

Melbourne was on its way to its hottest day since the devastating Black Saturday bushfires in 2009 with a maximum temperature of 44 degrees expected about 5pm.

The weather bureau warned gusty south-westerly winds would hit Melbourne on Tuesday afternoon, with a risk of thunderstorms producing dry lightning.

Mildura, in the state’s far north, was forecast to reach 49 degrees, while Broken Hill in NSW was expected to hit 47 degrees, with both locations set to break temperature records.

“If Mildura does reach [that high], it will be the hottest temperature recorded in Victoria,” senior meteorologist Dean Narramore said.

“Pretty much all observation points near the South Australian and Victorian border are either approaching or likely to exceed January records and a few locations could also break their all-time records.”

Ouyen, a rural township of about 1100 people in Victoria’s north, was also set to become one of the hottest towns on Earth, with a maximum of 49 degrees forecast for the afternoon.

There are statewide fire bans across Victoria and SA as multiple blazes burn out of control in the tinderbox conditions.

People in Gellibrand and surrounding areas south-west of Melbourne were advised to leave on Tuesday.

There were evacuations at Barramunga, Barwon Downs, Mount Sabine, Olangolah East, Tanybryn, Upper Gellibrand, Aire Valley, Beech Forest, Carlisle River, Chapple Vale, Charleys Creek, Crowes, Dinmont, Ferguson, Gellibrand, Glenaire, Johanna, Kawarren, Kincaid, Lavers Hill, Pile Siding, Simpson, Weeaproinah, Wyelangta.

Another emergency warning was issued for a fire near Camperdown in the state’s south-west.

It was too late to leave for residents in Kariah, Larralea, Leslie Manor, Lismore, Taaraak.

Mildura mayor Ali Cupper said the town’s forecast of 49 degrees was “unheard of”.

“If you’re out in the heat, a couple of degrees can be the difference between life and death,” she said.

The region is forecast to swelter through multiple days of 40 degrees-plus heat until cooler weather arrives from Sunday. Cupper urged locals to put out water for local wildlife, stay indoors when possible and monitor for the latest weather updates.

Emily Dalton, publican at Ouyen’s Victoria Hotel, said the heat had built steadily each day, with conditions especially punishing by late afternoon.

“By four or five o’clock, it’s tough to be outside,” she said.

The hotel has become a natural refuge as local businesses closed early while residents headed to the lake or the pub.

“Bring your dogs, bring your cats — the beer is cold and the food is good,” Dalton said.

The temperature in Adelaide reached 44.7 degrees on Monday, topping the city’s previous Australia Day heat record from 2006.

Ceduna, north-west of the state’s capital, climbed to 49.5 degrees, surpassing its previous record temperature, while NSW town Dubbo reached 46.1 degrees for its hottest January day.

A cooler change will begin to move through Victoria and South Australia on Wednesday.

However, inland parts of the south-east won’t get much of a reprieve, with temperatures in Victoria’s north expected to reach 40 degrees for seven days.

Deputy incident controller Alistair Drayton said the gusty change was worrying, with authorities urging residents living in Gellibrand and surrounding areas south-west of Melbourne to evacuate.

“The conditions mean the fire could spread quickly and unpredictably,” he said.

“We strongly recommend people in affected areas to enact their bushfire plan, and leave early to protect themselves and their families.”

The heatwave conditions have also sparked a warning from paramedics, who responded to 11 cases of children locked in cars over the weekend as temperatures soared into the 40s in Victoria.

-with AAP