A record-breaking heatwave is making its way across Australia with temperatures set to exceed 40C, & more in News in 5.

– With AAP. 

1. A record-breaking heatwave is making its way across Australia with temperatures set to exceed 40C.

A record-breaking heatwave is making its way across southeastern Australia, with temperatures set to exceed 40C in many parts of the country this week.

After Perth sweltered through three consecutive days above 40C at the weekend, Adelaide is now facing a four-day run that is expected to peak at 44C on Friday.

The extreme heat will reach the ACT, NSW and Victoria on Wednesday, with the Bureau of Meteorology expecting that inland parts of the territory and states will experience temperatures in the mid-to-high 40s.

A four day statewide total fire ban is in place in NSW as the heatwave moves through parts of the state still battling more than 100 bushfires on Thursday.

“We’re looking at temperatures during the daytime that are around 10C-to-14C above average for this time of year,” BOM acting NSW manager Jane Golding told reporters on Tuesday.

“With the heat comes fires, so we’re expecting some particularly tricky days for the fire response on Thursday, Friday, Saturday and Sunday.”

The bureau expects temperatures in many locations to approach or even break December, and potentially, annual records.

Climatologist Dr Blair Trewin said Australia may this week hit a record for its warmest day, exceeding the 40.3C average maximum temperature set in January 2013.

Victoria could record its hottest December day on Friday if centres in the northwest such as Mildura and Swan Hill reach a forecast 47C.

"We're expecting a lot of December records to be challenged, particularly in northwest, north-central Victoria some parts of northwest Victoria may get very close to records for any time of the year," Dr Trewin said.

Mildura is forecast to swelter through three days in a row of 45C and above.

"That's only happened once before in 1939 so it is certainly a very significant heatwave, particularly for December," he added.

In western NSW, temperatures are expected to climb above 45C, while Canberra is bracing for 43C on Saturday.

"For the ACT we're looking at five days in a row above about 37 degrees. Three of those days will be in the low 40s, so severe to extreme heatwave conditions," Ms Golding said.

Alice Springs is expected to reach 45C on Thursday, close to its hottest temperature of 45.6C, a record met twice last summer.

Parts of Queensland are still sweltering despite a cool change bringing relief to Brisbane after it hit 41.2C on Monday, its highest December temperature since 1981.

But the western town of Birdsville is forecast to remain in the mid-40s all week, peaking at 47C on Wednesday.

As the mercury climbs, authorities are warning people to prepare for the hot weather.

"Extreme heat kills more Australians than any natural disaster and can affect anybody, but those most at risk are older people, young children and those with medical conditions," Victoria's State Response Controller Gavin Freeman said.

He advised people to stay hydrated, keep cool, never leave kids or pets in hot cars and check in on others who may be at risk.

2. Police appeal for help to find seven missing siblings in Melbourne.

Seven Melbourne siblings are reported missing, prompting a Victoria Police call for public assistance.

Police have released images of four of the Fuimaono children, who are all believed to be with their mother June Paese.

There are serious concerns tonight for seven young siblings from St Albans, who vanished three weeks ago. @NearyTy_9 #9News pic.twitter.com/sWrVWtWiXg

— Nine News Melbourne (@9NewsMelb) December 17, 2019

The St Albans children are aged between two and 16 and those at school have not been seen there for at least three weeks.

"Police and family have concerns for the welfare of the children ... due to the length of time they have been missing," Victoria Police said in a statement.

3. A human leg has washed up on a beach on the NSW mid-north coast.

Police were called to North Beach at Mylestom, south of Coffs Harbour, after 2pm on Thursday following reports that human remains had been discovered by a member of the public.

Police have launched an investigation after a horrified beachgoer found a human leg washed up on the sand in NSW’s north coast.https://t.co/l2gpZwwWuY

— news.com.au (@newscomauHQ) December 17, 2019

Officers are currently on the scene and have commenced inquiries into the remains.

At this stage police do not know how the human leg came to be on the beach.

4. Two people stabbed to death in Sydney during a neighbourhood dispute.

Two people have been stabbed to death in a violent attack at a unit in Sydney's southwest.

Emergency services were called to Huntley Place in Cartwright about 4pm on Sunday following reports a man and a woman had been stabbed in a dispute.

The man died at the scene, while the woman died in Liverpool hospital despite the "valiant" efforts of paramedics to save her, Superintendent Adam Whyte told reporters at the scene.

Police have now confirmed two people have been stabbed to death in a violent attack at a unit in Sydney's southwesthttps://t.co/XV5SDGYagb

— SBS News (@SBSNews) December 17, 2019

"It appears that a male and a female have come to the units here in Cartwright in respect to a dispute and as a result of that a scuffle has broken out and unfortunately it has resulted in two persons being seriously injured and passing away from those injuries," he said.

A man is assisting police with their inquiries.

Supt Whyte has reassured the public they are not in danger, saying the attack was "specific" and not random.

He said police were still on the scene and trying to piece together what has happened, and were unable at this stage to comment on reports an axe had been involved in the killings.

5. A group of "critical" NSW koalas were saved from a bushfire.

A group of koalas considered "critical" to the future of the species has been saved in a daring rescue as a bushfire bears down on their NSW home.

The eight adult and four joey koalas from the Blue Mountains Kanangra-Boyd National Park are considered critical to the survival of the koala species due to their genetic diversity and the fact they're one of only two Australia koala populations that are chlamydia free.

The koalas' home is currently being threatened by the Green Wattle Creek fire which has already burnt through 140,000 hectares of parkland.

The animals were saved on Sunday by conservation group Science for Wildlife and taken to Taronga Zoo after authorities warned weather conditions were set to deteriorate.

"This week's forecast has multiple days above 40C in western Sydney with gusty and changeable winds, so it was important that we rescued these animals from impending danger," Taronga's Nick Boyle said in a statement on Tuesday.

A group of 12 wild koalas in NSW's Blue Mountains region has been saved from approaching bushfires, in what authorities are calling a "daring rescue" in the face of approaching bushfires https://t.co/EGPPflAk1B

— SBS News (@SBSNews) December 17, 2019

"We are committed to caring for these important koalas to ensure some of this vital genetic diversity from the Blue Mountains can be preserved and that the future of this iconic species is secured."

The koalas were retrieved in what was described as a "daring rescue" by Science for Wildlife director Dr Kellie Leigh.

"The national park is closed to the public due to fire risk but they gave us a two-day window when it was safe to go in in front of the fire," she said.

"These koalas are hard to find and catch, we wish could have saved more, but we're glad we could rescue this group. A lot of good people helped at very short notice."

An estimated 2000 koalas are feared to have already died after bushfires razed their natural habitat on the NSW mid-north coast.

Eight koala populations have had between 73 and 90 per cent of their habitat burnt "leaving them in particular danger of imminent collapse", a submission to a NSW upper house inquiry revealed earlier this month.

Feature image: BSCH.

Sign up for the "Mamamia Daily" newsletter. Your morning hit of the top news stories, to be consumed with a coffee in hand.