NSW lashed by intense thunderstorms

Quick-moving thunderstorms have swept through NSW, bringing large hailstones, heavy rain and flash flooding.

Trees brought down powerlines, houses were inundated and a family had to be evacuated as the storms moved across the Blue Mountains and western Sydney before travelling up to the mid-north coast and beyond.

The State Emergency Service (SES) received more than 200 calls for assistance on Saturday afternoon, including one from a Blue Mountains family trapped in their home.

The two adults and two children had to be rescued after water inundated their Hazelbrook house, SES spokesman Dave Owens said.

Most of the other calls related to damaged roofs and gutters, as well as damaged cars.

Residents reported hailstones around the size of a 20c coin that were "big enough to bruise" on the SES Facebook page.

The storms then moved on to Port Macquarie, where an intense storm felled several trees and brought down powerlines in the nearby town of Telegraph Point.

On Saturday evening, storms lashed Coffs Harbour, sparking 50 calls for assistance.

"The weather is very volatile at the moment," Mr Owens said, adding further thunderstorms were expected in NSW on Sunday.

By 8pm (AEDT), the Bureau of Meteorology (BOM) reported the storms had died down across the state but predicted there would be more on Sunday.

Meanwhile 6000 people remain isolated across the north of the state, with the SES monitoring flood water as it moves south.

An evacuation order was in place for 68 people in the Weilmoringle indigenous community, while an evacuation warning had been issued for the town of Goodooga.

The main flood peak in Namoi was expected to reach Goangra over the weekend with moderate to major flooding, according to the BOM.

Prime Minister Julia Gillard visited the flood-stricken town of Moree on Saturday as part of a tour to survey clean-up operations in NSW and Queensland.

The federal government was working closely with the NSW government to ensure affected communities were getting the necessary commonwealth assistance immediately, Ms Gillard said.

About 6,800 claims worth more than $8 million had been granted in NSW, she said.

"There's a lot to do here to keep supporting people, just as there will be a lot to do ... in Moree and wherever the flood waters have touched in Queensland and New South Wales," Ms Gillard told reporters in St George.