SES Superintendent Graeme Craig said there was a very rapid increase in the height of Kingdon Ponds after intense rain early on Friday morning, which led to major flooding.

"It was sitting at around 50cm overnight, now it's at 3.8 metres, which happened over couple hours," he said.

The SES had to perform three flood rescues in Scone - two from people stranded in cars, and one from a property that became surrounded by water.

Scone Race Club has also opened up for residents to use to shelter their horses or put them on higher ground.

The intense rain hit the Upper Hunter hard on Friday morning, and Superintendent Craig said it had created further challenges as some of the worst affected areas did not have rain gauges.

Six properties in Cassilis, including a police station, suffered inundation and had to be evacuated.

There have been more than 150 calls for assistance across the Hunter and Central Coast on Friday.

Superintendent Craig said the rainfall was starting to head downstream, and SES crews were "preparing for the worst, but hoping for the best" in the Lower Hunter, where a minor to moderate flood warning remains in place.

"We're prepared for all situations as that emerges over coming days," he said. "The rain hasn't been quite so bad in the lower end of the Hunter. There are risks of moderate floods, but with enough rainfall that can quickly become major."

Several major roads have been impacted, with Live Traffic NSW reporting the New England Highway at Wittingham is closed in both directions and a southbound lane of Maitland Road is shut at Hexham.

Heddon Greta Drive-in has cancelled all screenings on Friday and Saturday as the ground is completely waterlogged and very slippery and presents a safety concern.

"Besides, to be honest, we have only sold a handful of tickets," the drive-in wrote on Facebook. "Let's hope the rain is gone by next weekend."

The SES advises that people should:

• Move your car under cover or away from trees.
• Secure or put away loose items around your house, yard and balcony.
• Keep at least eight metres away from fallen power lines or objects that may be energised, such as fences.
• Report fallen power lines to either Ausgrid (131 388), Endeavour Energy (131 003), Essential Energy (132 080) or Evoenergy (131 093) as shown on your power bill.
• Trees that have been damaged by fire are likely to be more unstable and more likely to fall.
• Keep clear of creeks and storm drains.
• Don't walk, ride your bike or drive through flood water.
• If you are trapped by flash flooding, seek refuge in the highest available place and ring 000 if you need rescue.
• Be aware that run-off from rainfall in fire affected areas may behave differently and be more rapid. It may also contain debris such as ash, soil, trees and rocks.
• After bushfires, heavy rain and the loss of foliage can make the ground soft and heavy, leading to a greater chance of landslides.
• Unplug computers and appliances.
• Avoid using the phone during the storm.
• Stay indoors away from windows, and keep children and pets indoors as well.
• Stay vigilant and monitor conditions. Note that the landscape may have changed following bushfires.
• For emergency help in floods and storms, ring the SES (NSW and ACT) on 132 500.

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