Young family rescued after pleading for help from rising floodwaters

Sam and Jordan Halloran and their young son Zaphyr were trapped on the top floor of their Glenthorne property, near Taree.

"Is there someone with a boat that can ... come and get my wife and little boy in Glenthorne before our top floor goes under? (We've) Been waiting for 6.5 hrs," wrote Mr Halloran in one Facebook post early on May 21.

A video posted showed brown murky floodwaters enveloping the property. Cars can be seen already submerged in floodwater.

Hundreds of people tagged the SES in their post, and a couple of hours later, Mr Halloran's wife and son were airlifted out of the house via helicopter.

Mr Halloran and a neighbour were then rescued.

"Can't thank everyone enough for your kind words and efforts to help us," he posted after the rescue.

"Huge thanks to nsw police Rescue and the SES for getting us out safely. Now we wait to go home eventually, assess our losses, and start over. Big love x."

Rivers across eastern NSW are experiencing significant flooding, particularly the Manning River, Gloucester River, Williams and Paterson Rivers.

The Manning River is flooding at a level never seen before, surpassing the 1929 record of six metres. The SES has warned it has yet to hit its peak.

Heavy falls are occurring around the NSW Mid North Coast and will continue on May 21 as a coastal trough slowly tracks north.

The SES has forecast 24-hourly rainfall totals between 150 and 200mm.

Locations which may be affected include Coffs Harbour, Port Macquarie, Taree, Kempsey, Woolgoolga, Sawtell, Dorrigo, Wingham and Yarrowitch.

There were 103 NSW public schools and 19 independent schools closed as of 3.30pm on May 21. These include:

In the last 24 hours, NSW SES responded to 342 flood rescues, with the bulk of these in the Taree, Wingham and Glenthorne areas.

Around 290 of these flood rescues occurred since midnight.

The rescues included several cars caught driving into floodwater.

Some people are believed to be sheltering on the roofs of their properties, the SES said.

SES spokesperson Emilie Wells told ACM that more than 48,800 people have been isolated by floodwaters.

There are 109 flood warnings currently in place, with 19 at Emergency Warning level, 57 Watch and Act and 33 at Advice.

Residents in Kempsey CBD, Gladstone and Smithtown have been asked to evacuate this afternoon, as floodwaters continued to rise.

Ms Wells urged residents in low-lying areas to "stay vigilant and monitor warnings closely".

"If you are under emergency warnings and it is safe to leave, now is the time to go," she said.

"As night falls, rescue conditions become more dangerous."

Earlier this morning, NSW SES state assistant commissioner Colin Malone described the situation as "dynamic".

"Unfortunately, we've also had a large number of calls for help in areas that were subject to evacuation warnings, and we are still assessing how best to access those locations," he said.

"We've advised those people needing assistance to move to higher ground, as we're unable to currently access by boat, road or air due to the current weather conditions."

In one of the more significant incidents overnight, 24 people were rescued from the flooded Pacific Highway at Ghini Ghini.