THE emergency services are fed up with “total stupidity” in the aftermath of the NSW superstorm, pleading with people to use commonsense in floodwaters after a foolhardy teen had to be rescued, lucky to escape with his life after a daring bike ride.

Floods have already claimed four lives with fatalities related to accidents caused by the storm have doubled that toll.

Rescue crews conducted a swift-water rescue in the fast-flowing Nepean River in the middle of the night to rescue the 18-year-old, who’s now in hospital in a stable condition.

“I don’t know how he in got there, I don’t know why he got there,” NSW SES deputy commissioner Steven Pearce told ABC television on Thursday.

“But foolish actions are putting our people in danger as they do with other emergency services.”

Mr Pearce said people still needed to exercise caution due to ongoing flooding.

“I’ve seen vision this morning of cars still being caught or trapped in causeways — again total stupidity,” he told ABC TV.

LUNACY: A person is paddle boarding on Manly Dam. Please follow emergency warnings and don't enter dangerous areas. pic.twitter.com/6cy5pJmU0L — Chris Urquhart (@chrisurquhart) April 21, 2015

While the worst of the wild weather is over the extent of the damage this week’s killer east coast storm has caused is only beginning to be uncovered.

Storm-battered towns in NSW have been warned to watch out for more flooding and evacuation orders remain in place for parts of southwest Sydney after the Georges River broke its banks, forcing residents out of 250 Milperra homes.

The death toll rose to at least eight yesterday as Sydney, The Hunter and the Central Coast weathered a third day of record-breaking rain and cyclone-strength winds.

The latest victim of the flooding was confirmed on Wednesday night as police divers retrieved the body of an elderly woman whose car was washed away that morning.

Horrified witnesses could do nothing as the woman’s car was swept into Wallis Creek along Cessnock Road in the Hunter Region.

In accidents blamed on the storm a man died after his ute hit a garbage truck at Gaston and an 87-year-old pedestrian was struck by a car in East Gosford.

Two drivers were killed on the New England Highway in a head-on collision just after 3.20pm yesterday, with two passengers taken to hospital with serious injuries.

The horror accidents came as one of the worst-hit towns, Dungog, mourned the loss of three elderly people killed in the floodwaters on Tuesday.

Cyclonic conditions that have lashed Sydney and surrounding regions for days have left a trail of destruction, including more than 200,000 homes without power as of Wednesday evening.

Bureau of Meteorologist forecaster Jake Phillips said aside from some intense showers, the weather was easing.

“Showers will be nothing like what we’ve seen in the past few days,” he told AAP on Wednesday night.

Storm victims have been warned to be wary of floodwaters as they cleaned up their homes.

Premier Mike Baird applauded the tireless work of emergency services workers, including 800 SES volunteers who have responded to more than 10,500 calls for help in the past three days.

“They put everything on the line for our communities across this state and we are incredibly grateful for them and thank them for their continued work,” he said.

Mr Baird asked residents of Maitland and the Central Coast, who have borne the brunt, to “hang tough”.

“We are there to support you, and undoubtedly we still have some difficult hours ahead of us.”

Almost 100 SES volunteers from the ACT and Victoria have arrived to assist. NSW SES Commissioner Adam Dent warned the emergency was far from over and advised people to hold off on non-essential travel.

Roads in many areas remain flooded and power lines are down in affected areas. In the Central Coast and Newcastle, Hunter Region and South Coast, buses will replace trains in some sections and many ferry services are not operating.

Bus delays can be expected throughout Sydney, and while the airport is open, delays of up to an hour can be expected for domestic flights, with some international flights being diverted.

The Insurance Council of Australia has declared the storm a catastrophe, with expected losses of more than $129 million and rising.

By last night insurance companies had received more than 19,500 claims from customers for damage caused by trees falling on houses and cars, and leaking roofs.