Sydney storm cuts power, delays flights

Flights at Sydney airport have been delayed and thousands of homes left without power as a late afternoon storm hit parts of NSW.

Sydneysiders heading home from work have copped a battering on Tuesday with a severe thunderstorm bringing with it warnings of hail and flash flooding.

The inner-city suburb of Marrickville copped 33mm of rain in one hour between 5-6pm.

The State Emergency Service received 100 calls for help across Sydney, most of those for leaking roofs.

A handful were requests for sandbagging due to flash flooding across a number of suburbs, while two people had to be rescued in Arncliffe and Bexley.

Almost 5000 homes and businesses in western Sydney and the Blue Mountains were cut off from power, Endeavour Energy said in a statement.

Residents between Blackheath and Springwood had electricity cut off for about five minutes.

In Penrith, 1000 were without power while in Mount Druitt and Rooty Hill 440 homes were cut off.

Wollongong, Orange, Katoomba, Parkes, Dubbo and Bathurst were also warned to expect the deluge.

Some passengers at Sydney Airport were temporarily grounded due to lightning strikes and the heavy downpour.

Trains between Quakers Hill and Riverstone were cancelled with lightning strikes affecting equipment at Blacktown.

Commuters are being diverted on to buses.