Authorities are warning New South Wales' fire nightmare is far from over with fears spreading fires will cause "damage and destruction" before the night is over.
Twelve emergency warnings have been issued by the NSW Rural Fire Service (RFS) and the temperature in Penrith, in Sydney's west, reached 48.9C just after 3pm.
Highways have been closed and communities on the South Coast, the Snowy Mountains, and Sydney's doorstep have been urged to take shelter after conditions deteriorated.
Rural Fire Service (RFS) Commissioner Shane Fitzimmons warned a southerly change moving up the coast this evening meant things could get worse.
"Looking at where the fires are moving and spreading, I'll be surprised if we are not seeing reports of damage and destruction before the night is over," he said.
"It's going to be a very long afternoon and evening and, as that southerly approaches, it's going to be a volatile southerly with wind strengths up to 80kph or more.
"[It will mean] a long, difficult few hours."
Premier Gladys Berejiklian said there hadn't been any reports of lives lost but it was a "very volatile situation" and "we are yet to hit the worst of it".
"We are discouraging people from moving from where they are, given the serious threats and the fact that we have so many fires at an emergency level."
The Princes Highway, that connects Sydney and Adelaide, is closed in both directions near Jervis Bay and drivers in some places have been warned to avoid all non-essential travel.
Many of the emergency blazes were on the South Coast between Nowra and Bega, and the Snowy Mountains, where five out-of-control fires were also threatening properties.
The RFS warned a fire-generated thunderstorm had formed over one fire in the Snowy Monaro area creating a "very dangerous situation".
Closer to Sydney, the Green Wattle Creek fire in the Southern Highlands has also returned to emergency level.
That blaze has razed more than 264,000 hectares and residents have been told the fires pose "a serious threat to life".
While they are the most serious threats, the bigger picture in NSW is significantly more dire - around the state more than 130 blazes are stretching an estimated 3000 firefighters.
New South Wales Transport Minister and Member for Bega, Andrew Constance, has compared the South Coast fires to "an atomic bomb."
Constance said he had been out defending his home against ember attacks today, after fighting off a ferocious blaze earlier this week.
"I've got to be honest with you, this isn't a bushfire it's an atomic bomb," he told ABC Radio Sydney.
"It's indescribable the hell it's caused and the devastation it's caused."
The NSW death toll since the start of the bushfire season is 17, including eight since Monday and at least 449 homes destroyed on the South Coast since New Year's Eve.
Bushfires threaten dozens of Victoria communities
Army helicopters have been used to evacuate dozens of people from the fierce fire threat in Victoria, where more than 100 homes have been razed and towns remain at risk tonight.
Strong winds are continuing to push fires towards communities in Victoria's north-east and East Gippsland, where six people remain missing.
Authorities said at least 110 properties and 220 outbuildings had been lost - but the full scale of the damage is not yet known after thousands of people fled threatened communities.
"Our biggest concern at the moment is very significant fire activity in the north-east of the state," Premier Daniel Andrews said this evening.
"We have about 1000 firefighters on the fire ground, we are by no means out of this."
In the East Gippsland town of Omeo, residents have described seeing the sky turn red, and then black, as a fire front hit.
Around 50 people were evacuated from the town using Army helicopters after bushfire hit about 4:00pm.
Resident Brian Hadden said it went "red and black" as the main fire front hit, before helicopter evacuations began.
"Where I am at the Omeo Recreation Reserve, there is about six or seven big choppers, army and police," he told ABC Gippsland.
"I can see lots of wind and hell of a lot of smoke. It's been a hell of a day and a night."
Deputy chief fire officer Beth Roberts said authorities were working to juggle both firefighting and relief as they responded to the "unprecedented" bushfire emergency across East Gippsland.
"While we are absolutely concentrating on response, it is important for us to be looking at immediate relief and recovery," she said.
Late this afternoon, cooler temperatures reached East Gippsland. It dropped to 17C at Mount Nowa Nowa and 20C at Orbost, a dramatic drop from 40C earlier in the day.
Two deaths confirmed in South Australia
Two people have been killed in bushfires that have ravaged large parts of Kangaroo Island in South Australia, police have confirmed.
The deaths happened on the Playford Highway in the centre of the island.
Yesterday, the ABC posted a video on Facebook showing footage of a "fire twister" on Kangaroo Island.
While damage assessment is continuing, the ABC has confirmed several houses have been lost and there has been significant damage to the exclusive Southern Ocean Lodge hotel.
The threat on the western half of the island has been downgraded to watch and act but the fire is still out of control.
Up to 150,000 hectares - about a quarter of the island - has been burnt and authorities are warning of significant property losses.