Two women trapped underneath a collapsed roof in Western Sydney have been freed overnight after wild weather wreaked havoc across New South Wales.

Fire and Rescue NSW (FRNSW) were called to Bringelly, near Penrith, about 9:30pm on Wednesday to find the roof of a construction portable building caved in. 

The women were trapped for a short time before being freed by FRNSW crew.

Fireighters at the scene of a roof collapse

Fire and Recue NSW crews attend a roof collapse in Bringelly, near Penrith. (Supplied)

They were taken to hospital by paramedics and suffered minor injuries.

It comes as the NSW State Emergency Service (SES) received more than 850 calls for help and carried out 34 flood rescues over the last 24 hours.

There were 593 incidents and 34 flood rescues carried out across Sydney and parts of the state’s north-east, north-west and south-east.

The SES received the highest number of calls within a 50 minute period on Wednesday evening mostly related to water leaking into properties and vehicles stuck on flooded roads in Sydney.

Floodwaters reached the height of a tree

Rain has smashed Sydney and parts of the state’s north-east, north-west and south-east overnight. (Supplied)

In Sydney’s east, SES volunteers responded to 32 incidents and performed six flood rescues in Randwick.

Areas most impacted included Anzac Parade and Moore Park Road, with flash flooding stranding light rail passengers in the evening.

There were another 15 flood rescues performed in Maroubra, Kingsford, Coogee, Kensington, Moore Park, Alexandria, Waterloo, Paddington, Pyrmont, Ultimo, Redfern and Surry Hills. 

At Wattamolla, south of Sydney, volunteers rescued three bushwalkers in the Royal National Park just after 1pm on Wednesday, after they were inundated by flash flooding on their return route. 

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Kiara Magnussen from the NSW SES said the crew used a specialised rescue boat to successfully bring the group to safety. 

“The flood rescue operators traversed the river using an Ark Angel raft and they hiked 800 metres to get to where the bushwalkers were sheltering,” she said.

“They then walked the bushwalkers to safety and assisted them to cross the flood waters in the [raft].”

More heavy rain expected

As of 9am Wednesday, Obsevatory Hill recorded 104.8 millimetres of rain and 83.2mm fell at Sydney Airport, with wet weather and damaging winds set to continue through Thursday morning before easing, according to the Bureau of Meteorology (BOM).

In the state’s Hunter, Mid North Coast and Northern Tablelands regions heavy rainfall and damaging wind gusts up to 90 kilometres per hour are expected up until Thursday afternoon.

Floods of water at Parramatta

Parramatta Wharf on Thursday morning after heavy rains. (ABC News: Marcus Stimson)

Meanwhile, hazardous surf conditions will bring large and powerful waves to the northern and central coasts with an increased risk of damaging surf and coastal erosion.

Other parts of the state including the Illawarra, south coast and Southern Tablelands may face more heavy rain that could lead to flash flooding into Friday.

The BOM cancelled a severe weather warning on Thursday morning for the metropolitan area, Illawarra, south coast and Southern Tablelands.

A warning remains in place as of 8am Thursday, as heavy rainfall and damaging winds are expected to hit parts of the Illawarra, Mid North Coast, metropolitan area, south coast, Southern Tablelands, Northern Tablelands and the Hunter forecast districts.