A "mini tornado" has ripped through a Western Sydney suburb, tossing trees, ripping off roof tiles and spearing a trampoline into the side of a house.
Emergency services were called to Chester Hill about 8.30am on Saturday after reports of widespread storm damage across the area.
"Fire and Rescue Macarthur and Wollondilly crews are on scene in Chester Hill where a mini tornado has left a trail of destruction damaging multiple properties," the brigade said in a tweet.
More than 30 homes have been damaged, many partially collapsed, and power has been cut to much of the area, Fire and Rescue NSW said.
"Crews are working to remove trees, tarp roofs and conduct rapid impact assessments."
Photos of the damage show a trampoline with its legs impaling the side of a house.
The phenomenon was likely caused by intense localised rainfall, the Bureau of Meteorology (BoM) says.
Meteorologist David Wilkie said their systems picked up strong rotating winds, but the event may not have technically been a tornado.
"It's hard to say exactly what it was," he said.
"Whether or not it reached the kind of threshold you might term a tornado is certainly debatable but... looking at the damage it was obviously some pretty intense wind gusts that passed over the area."
The freak storm struck as a weather system that has sparked record flooding along the NSW coast headed towards Sydney.
Senior BoM climatologist Agata Imielska said Greater Sydney could expect about 100mm of rain over the next 24 hours or so, but the lower Blue Mountains is expected to get 200mm to 300mm.
Major river systems around Sydney are expected to see minor to moderate flooding, but major flooding is also a possibility, the bureau warned.
On the Mid North Coast, parts of Port Macquarie and several nearby towns have flooded. Evacuation orders are in place in many locations including Port Macquarie and Kempsey.
Further south, Taree is in the grip of a flood rivalling its worst event on record, 92 years ago.
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