Meteorologists said there were about 30,000 lightning strikes in the Hunter region overnight, with the area hit by "huge" hailstones reported to be about five centimetres in diameter.

The hail fell in Newcastle shortly before 4.30pm and lasted about 15 minutes.

The western reaches of the Hunter experienced hail about 4pm. 

In Gresford, there were reports of hail about five centimetres in diameter, which is classified by meteorologists as “huge” hail.

Weatherzone meteorologist Craig McIntosh said the storm was “widespread” across the Hunter.

“The rainfall as it stands is low, but there are pockets of heavy showers moving through the Hunter quite quickly,” he said.

“There are quickly changing winds and lots of lightning strikes.”

Mr McIntosh said a low pressure system moving across NSW was the cause of the unstable weather.

Hunter residents were urged to be mindful of changing weather patterns while the severe weather warning remained in place on Thursday.

The SES had about 30 call-outs for help in the Hunter by Thursday evening. By Friday morning the NSW SES had received 250 calls across the state, with a large amount from the Hunter region.

The majority were in Lake Macquarie with reports of flash flooding and hail damage.

“We’re urging people to stay safe on the roads and continue to monitor conditions,” SES spokesman Stephen Hart said.

More than 1000 homes in Anna Bay lost power during the storm and another 500 in Raymond Terrace.

Ausgrid was still working to restore power to some homes and businesses on Friday morning.

Weatherzone is owned by Fairfax Media, publisher of the Newcastle Herald.

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