Hail, wind and rain hitting NSW

Thunderstorms have struck NSW, bringing large hailstones, damaging winds and heavy rain.

The Bureau of Meteorology has issued a severe thunderstorm warning for Sydney, the Illawarra, Hunter, mid-north coast and upper western and northern tablelands.

The storm could lead to flash flooding and damaging winds.

A woman in the Macarthur area has reportedly been struck by lightning outside a primary school.

NSW Ambulance said paramedics were on the way to Oran Park after reports of a woman in her 30s suffered injuries from an electric shock.

Lightning also took out train signals in the western suburb of Granville.

About 17,000 people have lost power in Sydney's west and southwest, including in Minto, Fairfield, Wentworthville, Emu Plains and Kenthurst.

Stranded passengers at Sydney Airport have taken to social media to vent their frustration.

"Still sitting on the tarmac at Sydney Airport, an hour after we should have taken off. Thats quite the storm," one tweeted.