The Queen's public holiday is expected to be a wet one with a "near 100 per cent" chance of rain thanks to a low pressure system along the state's southern inland border, combined with a weak high pressure system in the Tasman Sea.

While the Hunter Region will cop a drenching, central NSW is bracing for further potential flooding with severe weather warnings in place.

The worst of the rain is expected on Wednesday, with six-hourly totals up to 70mm expected in the Central West Slopes and Plains and Riverina region.

The warning area covers a region stretching from south west of Dubbo through Parkes to Young and out to Narranderra.

IN THE NEWS:

Many catchments are already experiencing ongoing flooding from previous rainfall over the last few weeks, the Bureau of Meteorology warned on Tuesday.

Major flooding is possible along the Namoi, Macquarie and Lachlan Rivers and is already occurring at Wee Waa, Warren Weir and Euabalong on Tuesday afternoon.

People in Gunnedah in northwest of the state have already been hit with their third flood in a year with the State Emergency Service (SES) saying water inundated five houses on the weekend when the Namoi River peaked at just over eight metres.

The SES is warning residents at risk of flooding to prepare and plan with the ground already saturated and more heavy rain to come.

The agency has begun moving resources and equipment to areas of concern, including in the Central West and further north in the New England region.

There were three more requests for flood rescues overnight on Monday, on top of 30 over the weekend.

"With more weather coming from Wednesday we are concerned and are reminding the community to make sensible smart decisions when travelling at the moment," an SES spokesperson said.

- with Australian Associated Press