Updated February 18, 2017 16:55:48

Parts of Sydney and Wollongong are being hit with large hailstones as more severe thunderstorms with damaging winds and heavy rainfall lash the region.

The thunderstorms came a day after wild weather left thousands of homes in Sydney's north and on the New South Wales Central Coast face without power.

This afternoon the Bureau of Meteorology (BOM) warned that severe storms on the radar detected near Richmond could affect Hornsby, Sydney metropolitan area, Sydney Airport, Olympic Park, the Harbour Bridge and Liverpool.

A separate storm warning has been issued for storms detected near Kiama and Bowral, which are moving towards the east to south-east.

Residents in Sydney and Wollongong reported large hail, with one person on Twitter describing it as the "biggest hail I've seen".

The BOM's duty forecaster Steph Spackman said the storms were moving quickly.

"These thunderstorms are moving across the Sydney basin at a pretty good cracking pace of about 60 kilometres an hour and we do have a cell-based warning just to the east of Penrith," she said.

"We also have a very dangerous storm near Bowral with the possibility of destructive winds."

Ms Spackman said the storm over the Illawarra was very large and dangerous.

"We are expecting some heavy rainfall possible hail, especially to be careful of the one in the Illawarra region where we could get some quite significant weather effects from that very very large cell," she said.

"Everybody out there please be careful and take the proper precautions.

"We still have more instability over the Blue Mountains so once this passes over there is a possibility of more storms later this afternoon and evening."

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

After yesterday's storm, 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 per 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.

Topics: weather, storm-event, penrith-2750, campbelltown-2560

First posted February 18, 2017 16:07:11