Severe storms and strong winds have lashed Sydney and the NSW Central Coast, causing flash flooding, felling trees and leaving hundreds of homes powerless.
The State Emergency Service received hundreds of calls for help on Tuesday night and several roads were closed due to flooding, fallen trees and hanging wires.
The Bureau of Meteorology says a severe thunderstorm warning remains for the Central Tablelands, Southern Tablelands, Central Slopes Plains and South West Slopes.
"Giant hail, intense rainfall and damaging winds are all possible," the BOM said on Wednesday.
"Heavy falls leading to flash flooding is possible."
An SES spokesman said 400 volunteers responded to 370 incidents and performed 12 flood rescues overnight, mostly in Sydney's north and on the Central Coast.
Most of the jobs involved leaking roofs and flash flooding as well as trees that had crashed into homes and fallen across roads.
Several Manly ferry services were cancelled due to the large swell on Sydney Harbour and passengers were being advised to make alternative travel arrangements.
The SES was also called to help after an internal roof collapsed in a nursing home in the city's inner west.
The deluge hit Orange in the Central Tablelands and Queanbeyan, near Canberra, late on Tuesday afternoon before advancing on Sydney and surrounds in the early evening.
Orange recorded 38mm of rain in the 30 minutes to 3.30pm.
SES co-ordinator duty operations Neil Wiblin said Sydney's north shore, northern beaches and eastern suburbs copped the worst of the weather.
"The main type of jobs that we saw were trees and branches down due to the strong winds followed by roofs damaged and leaking and the heavy rain also caused localised flooding in a number of areas as well as road closures," he told ABC radio on Wednesday.
Some places recorded more than 100mm of rain, with Terry Hills in Sydney's north getting 121mm.
Ausgrid is warning fallen trees and power poles can camouflage electrical hazzards.
"If you see fallen wires, always assume they are live, never approach them, stay at least 8m away and call Ausgrid," it said in a tweet.
It says power is out in the southern suburbs of Caringbah, Miranda, Sylvania Waters and surrounds but has been restored to properties in Avoca Beach, Copacabana, Kincumber, Allambie, Allambie Heights, Manly Vale, Killara, Lindfield, Asquith, Eastwood, Hornsby and surrounding suburbs.
