Clean-up begins in Sydney after intense storms claimed the life of a man in the city's west

The clean-up is under way after a series of intense storms pummelled parts of Sydney, felling powerlines and trees.

One man died when the car he was travelling in was struck by a large tree at Emu Plains on Thursday.

The 60-year-old female driver of the car was taken to hospital in a critical condition with pelvic and abdominal injuries but is now in a stable condition, a hospital spokeswoman says.

Lightning strikes sparked three fires in the Blue Mountains and is also believed to be responsible for a fire at a power station.

READ MORE: Thousands still without power after intense storms

Strong winds also brought down powerlines, cutting power to more than 70,000 people in the city's north, south and western suburbs.

Trees also fell on a house and the roof of a nursing home, while others blocked roads.

The SES recorded more than 1200 jobs by late evening on Thursday, with the majority coming from the Sydney metropolitan region.

Mt Druitt, Penrith and Bankstown were the worst-affected areas, an SES spokesman told AAP.