A man is dead and a woman in a critical condition after a tree fell onto a car at Emu Plains in Sydney's west during Thursday's storm.
Severe thunderstorms carrying destructive winds lashed Sydney, after four major storm cells tracked a destructive path across city's west and southwest suburbs before passing through the eastern suburbs and out to sea.
Reports of extensive damage emerged on Thursday afternoon, with NSW police confirming a male passenger had died when a tree fell onto his car as it travelled east down Nepean Street in Emu Plains around 2pm.
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Man killed by falling tree in Emu Plains
A man is dead and a woman in a critical condition after a falling tree crushed a car in Emu Plains in Sydney's west during Thursday afternoon's thunderstorm.
The driver, a woman, was taken to Westmead Hospital in a critical condition.
By 4pm the storm cells had dissipated, and four new storm cells were moving through the Central Coast region, a spokeswoman from the Bureau of Meteorology said.
"They are pretty fast moving storms so the situation is rapidly changing," the bureau's severe weather meteorologist Miranda Langton said.
"It started out west and moved south east towards the coast. That line of thunderstorms is now gone and a new line has developed over the Central Coast."
NSW Police said the storm had caused extensive property damage to cars and houses in Emu Plains and Penrith as it hit the area about 2pm. Powerlines were also damaged.
Residents of Villawood, 25 kilometres south of Sydney, have also reported extensive damage, with photos showing panelling has been ripped from the roofs of businesses and scattered across a main street.
Destructive winds reaching speeds of 96km/h were recorded at Camden Airport just after 2pm, while, an hour later, Sydney Airport recorded gusts of 122km/h.
The State Emergency Service advised that people should move cars under cover or away from trees, secure loose items around houses, keep clear of fallen power lines, unplug computers and appliances, avoid using the phone during the storm, stay indoors away from windows, and keep children and pets indoors as well.
The destructive weather followed a day of severe heat across the Sydney region.
Sydney temperatures reached a peak of 39.2 degrees at 12.45pm in the city.
Reaching its own peak a little later, Penrith in Sydney's west hit 40.7 degrees by 1.45pm.
Weatherzone meteorologist Tristan Meyers said one of the reasons the urban heat island of western Sydney "sizzles on days like today" is that the city's sea breeze lacks strength.
"The sea breeze that forms along the coast often doesn't have enough strength to reach that far inland, so if you think of it as a fight between two winds: a land breeze and a sea breeze, the sea breeze isn't strong enough to overcome the land breeze in the western suburbs."
Heat blasts Sydney before dramatic change
Temperatures will hit close to 40 degrees across most of Sydney before rain and wind is set to make peak hour dangerous for commuters.
By midday on Thursday, data analyst Joel Kitson said he was "hiding" in his air-conditioned office from the soaring heat outside.
"Thankfully our building management have put it on maximum cold so people are actually complaining that it's freezing," Mr Kitson said.
"They've obviously tried to overcompensate by trying to put the air-conditioning down to something ridiculous."
Mr Kitson said he even ordered a hot tea to "warm up" but was planning to stay in air-conditioning for most of the day.
"I have to duck out to get the train, but I'll try to minimise my time in the station because for some reason it isn't air-conditioned. Hopefully, I'll time my trip perfectly so that I can just get straight on."
Once the cool change comes, gusty winds in excess of 60km/h and stronger are expected.
"It will be quite dramatic," Mr Meyers said.
Mr Phillips said the exact time of the change will depend on "where you are in Sydney, but you'll get it between 5pm and 7pm. And then we are still expecting some rain and quite likely thunderstorms".
Sydney's coastal suburbs will feel the change most intensely, where beach winds are expected to be extremely gusty.
Until the change comes, people are advised to visit air-conditioned spaces, drink plenty of water and keep out of the sun.
Heat expert and president of the Climate and Health Alliance, Elizabeth Hanna, said while people understand that the elderly and young children are at risk, many fail to realise that we are all vulnerable to heat.
"We know that people don't drink enough, and our new research shows workers significantly overestimate their capacity to keep working in the heat, meaning they're not as cautious as they need to be."
Rain will fall overnight and into Friday, tending to showers and bringing a much cooler day, topping at 21 degrees.
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