Australia Weather News

Thousands of homes in Sydney's north and on the New South Wales Central Coast could be without power for the weekend, as crews frantically work to restore supply ahead of another storm this afternoon.

The SES received 625 calls for assistance with fallen trees, branches and powerlines coming down on roads and houses mostly across Sydney, the Central Coast and the Hunter.

Hail, heavy rain and gusts of wind up to 109 kilometres an hour battered the region, leaving more than 40,000 homes in eastern New South Wales without power earlier this morning.

About 10,000 homes are still cut off — mostly in Sydney's northern beaches and on the Central Coast.

Ausgrid spokeswoman Phillipa Wheeler said some areas would not have power restored until tomorrow.

"This is a major storm event for our network area and the damage is extensive — they're restoring the major power lines first," she said.

The Bureau of Meteorology (BOM) warned that severe thunderstorms with damaging winds and large hailstones were detected on the weather radar near Kangaroo Valley and Nowra, moving towards the east.

The storms were forecast to also affect Gerringong, Kiama and Robertson.

The bureau said thunderstorms were also likely in the Illawarra and parts of Sydney, the Central Tablelands and Southern Tablelands districts.

Residents are being advised to clean gutters, remove outside furniture, place cars under cover and shelter inside with any pets when the storms hit.

Ausgrid received more than 400 reports of dangerous hazards on the network including fallen wires and trees damaging power lines. Multiple lightning strikes and falling trees caused serious damage to electrical infrastructure.

"Crews will be working as quickly as they can but it is likely that some small pockets of areas and some individual customers will be without power well into the weekend, possibly into Sunday," Ms Wheeler said.

"Crews have to go to those sites and make sure that area is safe for the public to be around, there is obviously live electrical equipment that we need to make safe if wires are on the ground.

"So once crews have made the area safe, they'll work to get the power on as quickly as they can."

Sydney's west was one of the hardest hit, and Canada Bay SES Unit Deputy Controller Bill Hoyles said it was the worst storm he had seen in 17 years on the job.

"We've had some really big trees come down across backyards down on roofs, a lot of roof damage," he said.

"With such a large number of jobs it may take time to get to some of those jobs, but we will get round to you as quickly as we possibly can."