One bushfire is burning in Penrith but it is under control.
New South Wales officials have said 600 firefighters remain on standby waiting to tackle any fires that may arise as temperatures across the state are forecast to reach up to 43 degrees today.
Authorities have warned that the intense heat, paired with strong winds are the recipe for extreme fire danger with total fire bans put in place across Greater Sydney to minimise fire risk.
The Saturday fire ban comes after NSW fire danger rated five districts as extreme risks, including in the Sydney area.
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NSW Rural Fire Service Commissioner Trent Curtin said that 600 firefighters are ready to be deployed across the state and "are prepared to respond to fires throughout the day".
"We have around 50 aircraft that are either currently deployed or that are ready to respond immediately right across the state," he said.
"That includes four heavy helicopters and three large air tankers. We have an additional 150 aircraft that we can employ if we need to across New South Wales today."
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The NSW Rural Fire Service is dealing with 44 fires, four of them uncontained.
That includes a grass fire at Range Road, Mummel, Goulburn at watch and act level.
Curtin said that communities need to remain alert to conditions across the state today and minimise travel where they can.
Temperatures hit 27 degrees in some parts of the city as early as 5.30am.
Sydney Airport peaked at around 42 degrees, with Penrith similar.
But the hottest was 43 degrees at Sydney Olympic Park in, Homebush, one degree short of an all time record.
NSW Premier Chris Minns has alerted people to stay vigilant as Sydney's heatwave comes to a head today.
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"We do lose people on these incredibly hot days," Minns said.
"People die as a result of extreme heat in Australia and we need to make sure that people are taking the kind of precautions that will keep them alive during a very hot day like the one we're seeing."
The premier also said that he is "concerned" about the more than 30 music festivals taking place today.
"I want to make it very clear that it's the responsibility of the organisers of those music festivals to provide shade and water for participants and those who are attending the music festivals."
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Minns also said Park Run events and cricket games were cancelled in some parts of the state as a result of the extreme heat.
A cooler change is set to come almost immediately, with temperatures of 26 degrees and rainy conditions forecast to roll in tomorrow.
Thunderstorms are also set to develop with wet conditions slated for the entirety of next week.
People heading to waterways to beat the heat are being urged to remain safe after a four-year-old boy died overnight after he was pulled unconscious from a pool on the NSW mid-north coast.
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