What makes Saturday's bushfire forecast so devastating

The impending extreme weather conditions are expected to be worse on Saturday than on New Year’s Eve when bushfires claimed several lives across Australia’s southeast.

NSW Rural Fire Service Commissioner Shane Fitzsimmons said Saturday's conditions affecting the state’s southwest and Victoria’s east would ramp up the danger levels across a region already ravaged by pre-existing fires.

So far 382 homes have been lost on the NSW south coast while 50 have been destroyed in Victoria. Both figures are expected to rise considerably as assessments of decimated areas continue.

The conditions are particularly dangerous thanks to unrelenting heat in the mid-40s, which will arrive thanks to a hot-air mass moving east across Australia.

The extreme heat will then be paired with a strong southerly arriving late on Saturday, which could reach well beyond 100km/h – a devastating combination, Bureau of Meteorology senior meteorologist Jonathan How told the ABC.

“Saturday is shaping up to be an extremely dangerous day,” he said.

“We’re expecting conditions to be as bad, if not worse, as what we saw on New Year’s Eve.”

On Saturday temperatures in the towns of Bega and Nowra are expected to reach 43C.

Mallacoota, where the evacuation of thousands of trapped locals and holidaymakers commenced on Thursday, will hit 41.

While crews tirelessly battle blazes in the south, the RFS will also be keeping a close eye on Sydney and its surrounding areas with temperatures in the west at Penrith predicted to hit 44.

Mr How said the conditions were particularly dangerous due to the late arrival of the southerly on the south coast about 5pm to 6pm.

It will arrive in Victoria’s east mid-afternoon.

“It is expected to come through later than what it did on New Year's Eve. With the later change it does mean there is more time for the landscape to really heat up,” he said.

“So a very dangerous day for these communities.”

Due to existing fires already burning, more fires are expected than on New Year’s Eve.

NSW RFS Commissioner Shane Fitzsimmons said the conditions and larger quantity of fires would be extremely challenging for exhausted crews tackling the blazes along the south coast.

NSW Transport Minister Andrew Constance, who lives near Batemans Bay, called the current situation “unprecedented”.

During a press conference on Thursday afternoon, Victorian authorities also said the upcoming conditions were “quite unprecedented in this state”.

Tourists told to leave before it’s too late

The NSW Rural Fire Service has established a “tourist leave zone” stretching 250 kilometres from Batemans Bay down to the Victorian border, with visitors and some residents urged to evacuate while they have the chance.

"Our message is as soon as the roads are able to be traversed we are encouraging, particularly holidaymakers and visitors, to make their way out to safer places like Sydney," Mr Fitzsimmons said.

Extensive queues began to develop along the Princes Highway early on Thursday with authorities urging for people to remain calm.

“We are anticipating heavy traffic out of these areas, so I want to remind all road users to expect delays – but be patient, remain calm, and drive to the conditions – we want everyone to make it out safely,” NSW Police Deputy Commissioner Gary Worboys said.

There were reports on social media of people waiting up to five hours to purchase fuel to leave.

On Thursday morning, there was 110 fires burning across NSW with over 50 yet to be contained.

So far 17 people, 15 in NSW, have died during the current bushfire season.

Victoria Premier Daniel Andrews confirmed 17 people remain unaccounted for following the latest fires.

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