A man was killed by a flying gas bottle in Sydney's The Rocks as severe thunderstorms hammered parts of New South Wales overnight.

Key points: A man was fatally injured by a gas bottle flying through the air during the storm

A man was fatally injured by a gas bottle flying through the air during the storm There were power outages and property damage across the state, as storms hit Sydney's metropolitan area, Wollongong and Orange

There were power outages and property damage across the state, as storms hit Sydney's metropolitan area, Wollongong and Orange About 65,000 customers remain without power this morning

Police said the 37-year-old man was walking along Harrington Street at about midnight when he was struck in the shoulder by a 9kg gas bottle.

He was taken to a nearby hotel by witnesses, before emergency services arrived at the scene.

He was treated for hand and chest injuries but went into cardiac arrest and was taken to St Vincent's Hospital but could not be revived.

NSW Ambulance Superintendent Kath Rallings said it was a "freak accident" and a tragedy for his family and friends.

"While this appears to be a one-in-a-million accident, please do not underestimate these wild weather conditions," she said.

This tree in Ultimo was uprooted during the wild weather. ( ABC News: Riley Stuart )

Police said they believed the man, from Chatswood, had been out for a few drinks after work, and appealed for people to check their balconies for any missing bottles.

"It is vital for us to know where the bottle has come from," said Detective Inspector David El-Badawi.

Spectacular lightning lit up Sydney's night sky with property damage in parts of the state and widespread power outages.

Severe thunderstorm warnings were issued for a large part of NSW last night, including Sydney's metropolitan area, Wollongong and Orange.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 11 seconds 1 m 11 s Trees were uprooted and roofs blown off houses as lightning strikes and wild wind pummelled Sydney

The NSW State Emergency Service (SES) said it received 906 calls overnight.

Ausgrid said 80,000 customers lost power during the night, with 66,000 getting power restored today across affected areas including the northern suburbs, northern beaches, the Central Coast, Hunter Valley and Newcastle.

Endeavour Energy said 10,500 customers remained without power, as it worked on 330 electrical hazards across Western Sydney and the Hawkesbury.

A fallen tree in Ocean Street North, Bondi Beach. ( Twitter: @GraziaOliva28 )

Wind gusts as high as 111kph were recorded at North Head, 104 kph at Fort Denison and 102 kph in Richmond, while the Bureau of Meteorology (BOM) issued an alert for dangerous driving conditions.

Tuncurry on the Mid-North Coast was battered by 2.8cm diameter hail, the BOM said.

Nowra Airport saw gusts of wind at about 90kph and 50mm of rain between 8:00pm and 9:00pm on Tuesday.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 1 m A roof was blown off from a house in Belmore damaging nearby vehicles

Elsewhere in the state, large hail was reported near Wollongong and Mittagong, while more hail and heavy rainfall was expected to impact parts of the Hunter, Mid-North Coast, Illawarra and Sydney.

Sydney Trains said severe weather conditions had caused delays to services, with lightning strikes affecting infrastructure as well as trees on the line in multiple locations.

Lightning streets in the backdrop of a Kurnell street last night. ( Glenn Campbell )

Ausgrid warned people to stay away from fallen power lines and stay at least 8 metres back.

The BOM reported destructive winds near Gilgandra, north of Dubbo, resulting in major property damage around 11:30pm.

A severe thunderstorm warning for Wednesday for damaging winds, heavy rainfall and large hailstones for the Mid-North Coast, North West Slopes and Plains and Northern Tablelands has now been cancelled by the BOM.

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