Some 180,000 homes have been left without power in Sydney and across New South Wales after storms battered the Australian state.
Winds of up to 135km/h (85 mph) were recorded in some areas, with up to 200mm of rainfall forecast for Tuesday.
A man is believed to be missing in floodwaters in Stroud to the north of Newcastle.
The State Emergency Service (SES) said it had received nearly 3,000 calls for help, with 19 flood rescues.
The agency said that most of the calls had come from Sydney and the regions of Hunter, Central Coast and Illawarra.
SES Deputy Commissioner Steven Pearce told ABC News that the number of calls for help had been “enormous”.
“We haven’t seen this sort of weather pattern, this east coast low or one as severe as this in years,” he said.
“The consistent gale force winds which are actually cyclonic in some areas with gusts up to 135km/h.”
The strongest winds overnight were recorded at Norah Head in the Central Coast region.
Meanwhile, 312mm of rainfall had fallen in Dungog in the Hunter region since Monday morning.
Local Fire and Rescue NSW said that crews were searching for a man who went missing after a camping ground was flooded in Stroud.
On Tuesday, a severe weather warning remained in place for damaging and destructive winds, heavy rain and damaging surf.
The areas affected are the Metropolitan, Hunter and Illawarra districts. Beach conditions in these regions are said to be particularly dangerous.
State-owned supplier Ausgrid tweeted that some 180,000 homes and businesses were without power across Sydney, Central Coast and Hunter.
But it added that crews were repairing fallen power lines at several locations.
The heavy winds and rain have also caused travel disruption in Sydney.
The Transport Management Centre for NSW said that staying home may be the best option for many people on Tuesday.
“If you don’t need to be out on the road, probably best not to be,” said spokesman Brett Moore, as quoted by ABC News.
A number of main roads and railway lines have had to be closed because of the storm.