Emergency services say the conditions surrounding more than 130 bushfires in one Australian state have reached "catastrophic" levels.
The term is used to describe a situation where fires are uncontrollable and fast-moving, with evacuation the only safe option.
“We are shaping up for one of the worst fire danger days on record,” New South Wales Rural Fire Service Commissioner Shane Fitzsimmons said.
“You don’t get conditions worse than this. We are at the catastrophic level and clearly in those areas leaving early is your safest option.”
Forty of the fires across New South Wales are uncontained.
There have been no reports of injuries or damage to homes so far, although officials in Tasmania were still trying to find around 100 residents who have been missing since a blaze tore through the small town of Dunalley, east of the state capital of Hobart, last week, destroying around 90 homes.
Today, police said no bodies were found during preliminary checks of the ruined houses.
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Firefighters have already evacuated national parks.
Daytime temperatures have hit 45C, and have stayed up around 38C in some areas right through to midnight.
Many residents and tourists in Sydney have taken to the sea to try to cool off.