A warning has been issued ahead of severe storms across eastern NSW, including Sydney, on Friday afternoon.
Severe thunderstorms are likely to produce heavy rainfall that may lead to flash flooding and damaging winds over the several hours.
The Bureau of Meteorology says a trough interacting with a warm and humid tropical air mass in the state's east, ahead of a low pressure system in the southwest of the state, will generate thunderstorms.
"Severe thunderstorms are likely to produce heavy rainfall that may lead to flash flooding and damaging winds in the warning area over the next several hours," the bureau said in a bulletin at 11.31am.
Locations which may be affected include Newcastle, Gosford, Sydney, Wollongong, Canberra, Goulburn and Tamworth.
Friday’s warning comes after wild weather on Thursday night left about 40,000 properties were left without power and a number of major roads were flooded as severe thunderstorms moved across the city.
The State Emergency Service (SES) conducted seven flood rescues after motorists became trapped in cars.
"The message we are trying to get out today is to not drive through floodwater; there are more heavy rains forecast so we want people to avoid unnecessary travel," NSW SES media officer Phil Schafer said.
The SES also responded to hundreds of calls for assistance, mainly for damage to roofs, fallen trees and flooding.