The flood crisis gripping NSW has now claimed eight lives after two bodies were found in floodwaters in western Sydney, as the coast is battered by unrelenting torrential rain with tens of thousands of people under evacuation orders.

Premier Dominic Perrottet says 40,000 people around NSW are under 59 evacuation orders, including orders in close to 40 suburbs around Greater Sydney.

There are multiple flood warnings for vast swathes of NSW and many roads, bridges and schools are closed.

About 2000 people in low lying areas near Manly Dam in Sydney’s north will likely be told to evacuate on Tuesday afternoon.

NSW SES Commissioner Carlene York said the dam is spilling, but not at risk of failing.

Northern Beaches Council Mayor Michael Regan told ABC News relocation centres had been set up in anticipation at the former Seaforth TAFE and Freshwater surf club.

The Bureau of Meteorology warned dangerous thunderstorms were likely to hit in Sydney’s north on Tuesday afternoon and could cause further flash flooding.

More than 128mm of rain fell at Mosman in the six hours to 12.30pm and 93mm of rain hit Mona Vale over three hours on Tuesday afternoon.

Police have called the deaths of two people killed in western Sydney a “tragic reminder” for people to keep off the roads as NSW suffers through dangerous weather.

Detective Superintendent Paul Devaney said the Wentworthville canal where the mother and son were found on Tuesday “rose this morning from ankle deep to above neck height in a matter of minutes”.

The victims are believed to be 67-year-old Hemalathasolhyr Satchithananthamand and her 34-year-old-son Bramooth who had been missing in the area after their car was found in the stormwater canal on Monday.

Efforts to recover the bodies were hampered by the weather in an operation that involved police divers, the rescue squad, assistance from the State Emergency Service and PolAir.

The first person was found about 1.4 kilometres from the car, and the second was found about 900 metres away.

The SES received more than 2500 calls for help in 24 hours and undertook about 200 flood rescues, mostly in Sydney.

The city has endured 16 consecutive days of rain and no reprieve from the deluge is expected until Wednesday, with no sign of sun until Thursday.

Wind gusts of up to 90 km/h are forecast, stretching south to the Illawarra region into Wednesday, and there’s a risk the winds could topple trees and down powerlines.

The Hawkesbury-Nepean catchment in Sydney’s west is experiencing floods as bad as or worse than those seen in March last year, the bureau’s Dean Narramore said on Tuesday afternoon.

The severity will depend on how much more rain falls in the next 12 hours.

He advised residents stay inside and up to date with flood warnings and evacuation orders.

Footage shared to social media as rain lashed Sydney on Tuesday has shown water pooling in the Harbour Tunnel, parts of the shopping centre roof collapsing at Bondi Westfield, and cars trapped as heavy rain flooded parts of the Roseville Bridge.

More than 30,000 insurance claims have been filed around NSW, the Insurance Council of Australia said, with the expected cost of the floods in Queensland and NSW now approaching $1.5 billion.

Some could be waiting weeks to have their claims assessed.

Sydney Trains is expecting significant delays and cancellations on most services due to the severe weather.

Drivers are also being asked to stay off the road unless necessary, with the sustained wet weather opening potholes and causing flash flooding.

The Illawarra Highway was closed on Tuesday between Moss Vale and Robertson in the Southern Highlands after a sinkhole formed under the road at Burrawang, NSW Police said.

NSW LiveTraffic tracker shows close to 400 warnings for flood affected roads.

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