Australia Weather News

A severe thunderstorm has hit Sydney and other parts of NSW, causing flight cancellations and leaving thousands without power.

By 8:30pm on Wednesday the State Emergency Service had received more than 100 calls for help, with authorities estimating about 4,000 homes across the state were without power.

By 10pm about 850 homes were still without power.

Delays of almost an hour hit Sydney Airport, however all runways were operational.

A spokesperson said seven domestic flights at the airport were cancelled.

The centre of the storm rolled over the city about 8:00pm, bringing lightning and heavy rain.

The small town of Clarence, about 120km west of Sydney, was the hardest hit, receiving 59mm since 9:00am on Wednesday morning.

Sydney's summer has kicked off with regular thunderstorm activity, with the last major storm rolling through on Saturday.

Warnings remain

Earlier in the day the Bureau of Meteorology put a warning in place for parts of central west NSW, the Blue Mountains region, Gosford/Wyong and Sydney areas, with large hailstones, damaging wind and heavy rainfall expected.

The warning applies to those people in the Central Tablelands, Central West Slopes and Plains and parts of Hunter, Illawarra, Southern Tablelands, North West Slopes and Plains, South West Slopes.

The Bureau of Meteorology said Orange, Tamworth, Gunnedah, Dubbo, Parkes, Yass and Tarlga may be affected and people in those areas should stay inside.

Further east, another warning is in place with Richmond, Windsor and Riverstone, Hornsby, Calga and Gosford.

This afternoon, Mudgee, in the central west, received 33 millimetres in just half an hour and Merriwa, in the upper Hunter shire, was hit by gusts of 114 kilometre per hour.

"Thunderstorms are likely to move toward the coast with a few rumbles and showers expected to the Illawarra through to the southern parts of the mid-north coast," Ms Duma said.

Overnight the storm activity is expected to ease but will likely re-develop tomorrow morning or afternoon leading to more storms over eastern parts of NSW, the BOM said.