Sydney and the Hunter region were battered by thunderstorms overnight with heavy rain continuing into the morning, causing flooding and damage.
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 NSW State Emergency Service received 250 calls for assistance overnight, with the Hunter and Sydney metropolitan region the worst affected areas.
Sydney commuters face a slow trip into work on Friday morning with wet roads and flooding in parts of the city, including Drummoyne, Moore Park and Beaconsfield. Trains between Sydney and Newcastle were also affected due to power supply problems caused by the weather.
Graeme Brittain, a senior meteorologist at Weatherzone, said heavy rain fell over a wide area of Sydney on Thursday night and early on Friday as a series of storm fronts moved across the city.
Little Bay in Sydney's east received a dumping of 32 millimetres of rain, Chatswood received 27 millimetres and Campbelltown 26 millimetres.
"The showers will continue for a few hours throughout the morning as the storm passes," Mr Brittain said.
"Conditions will gradually clear throughout the rest of the day."
He said there were 30,000 lightning strikes in the Hunter region overnight. Storms also passed over Sydney throughout the night, although there were significantly fewer strikes than in the Hunter, which bore the brunt of the bad weather.
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.
???A low pressure system moving across NSW is the source of the unstable weather which comes after a lengthy dry spell across much of NSW.
The Bureau of Meteorology is forecasting clearing conditions later on Friday, followed by a partly cloudy day on Saturday with a top temperature of 27 degrees.
A top of 29 degrees and mostly sunny conditions are forecast in Sydney on Sunday, rising to a top of 30 degrees on Monday.
Around 250 emergency calls to SES overnight, Hunter, Metro worst affected, no significant damage. Need emergency help? Call 132500.??? NSW SES (@NSWSES) October 26, 2017
Weatherzone is owned by Fairfax Media, publisher of the Sydney Morning Herald.