Bushfires raging across Australia are generating so much heat they are creating their own storms, with authorities warning wind conditions are causing some of the biggest fires to merge.
Fire tornadoes and dry lightning have sparked even more blazes, as temperatures soared to new highs today - 48.9C (120F) in Penrith, 45C (113F) in Sydney and 44C (111F) in Canberra.
Penrith, a suburb of Sydney, was the hottest place on Earth on Saturday, the Met Office confirmed to Sky News. It was the hottest day ever recorded in greater Sydney.
The New South Wales Rural Fire Service has updated emergency warnings, telling those who have not evacuated at-risk areas: "It is too late to leave. Seek shelter as the fire approaches."
Prime Minister Scott Morrison said: "In recent times, particularly over the course of the balance of this week, we have seen this disaster escalate to an entirely new level."
Victoria had 14 fires rated at emergency or evacuate warning levels on Saturday evening, while New South Wales had 11 rated emergency and more than 150 others burning across both states.
NSW Rural Fire Service Commissioner Shane Fitzsimmons said: "There are a number of fires that are coming together - very strong, very large, intense fires that are creating some of these fire-generated thunderstorms.
"And unfortunately we've still got many hours to go of these elevated and dangerous conditions."
Posting on Instagram, the Duke and Duchess of Sussex sent their thoughts to those affected by the fires.
Prince Harry and Meghan wrote: "Our thoughts and prayers are with those across Australia who are continuing to face the devastating fires that have been raging for months.
"From areas we are personally connected to such as the communities and people we visited in New South Wales in 2018, to the fires in California and parts of Africa, we are struck by the increasingly overlapping presence of these environmental disasters, including of course the destruction of the Amazon which continues.
"This global environmental crisis has now been described as Ecocide. It's easy to feel helpless, but there's always a way to help."
They also directed their followers to sites they have used to help the relief effort.
The Queen also sent a message, saying she was "deeply saddened" to hear of the continued fires.
She added: "My thanks go out to the emergency services, and those who put their own lives in danger to help communities in need.
"Prince Philip and I send our thoughts and prayers to all Australians at this difficult time."
Winds of up to 80mph are fanning the strength and unpredictability of the fires, with many places facing their worst day yet.
"We are in for a long night and we are still to hit the worst of it," New South Wales premier Gladys Berejiklian said. "It's a very volatile situation."
The storm conditions are caused by pyrocumulonimbus clouds - thunderstorms formed from the smoke plume of a fire that causes air to rise rapidly and collide with ice particles in the higher, cooler air, and building up electrical charges that create lightning.
Rising air also produces intense updrafts that suck in so much air that strong winds develop - making fires hotter and spreading them further and faster.
The phenomenon is expected to become more frequent in Australia as the global climate changes, according to a 2019 report by the country's Climate Council.
On Monday, a firefighter was killed when a pyrocumulonibus cloud formation collapsed and flipped over his 10-tonne truck. The total number of people killed since the fire season began is 23 - 12 from this week alone, with six people missing in the state of Victoria.
Australia's government has called up 3,000 reservists and committed $20m AUS to hire four special fire-fighting aircraft. A third navy ship with disaster and humanitarian relief equipment has been deployed, while the first of those rescued from a beach in Mallacoota arrived in Melbourne after a 20-hour sea journey.
US singer Pink has pledged $500,000 to help fire services battling on the frontlines. She tweeted: "I am totally devastated watching what is happening in Australia right now with the horrific bushfires.
"I am pledging a donation of $500,000 directly to the local fire services that are battling so hard on the frontlines. My heart goes out to our friends and family in Oz."
Firefighters say some areas cannot be defended.
Sky News' Alex Crawford witnessed the fires from a helicopter, where she said visibility was almost at zero in white-outs caused by the smoke.
"There's a lot of anxiety here, a lot of fear," she said. "I've seen a lot of posters thanking the firefighters, who are doing their utmost to contain these raging fires."
New South Wales Rural Fire Service Deputy Commissioner Rob Rogers warned the fires could move "frighteningly quick". Embers carried by the wind had the potential to spark new fires or enlarge existing blazes.
"We still have those dynamic and dangerous conditions, the low humidity, the strong winds and, what underpins that, the state is tinder dry," Victoria Emergency Services Commissioner Andrew Crisp said.
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One fire on Kangaroo Island, which has killed two people, has broken containment lines and been described as "virtually unstoppable" as it roared through 14,000 hectares (35,000 acres) of national park.
Professor Ray Wills, of the University of Western Australia, produced a map that showed the size of the area burned by fires, if transplanted to the UK, would have scorched most of England, from the south coast to almost as far north as Leeds.