Woman drowns in floodwaters near Gulgong, as elderly couple and dog rescued from Moama

A desperate search for the woman occurred overnight, after after a vehicle she was travelling in was swept into floodwaters near Gulgong, around 30 kilometres north of Mudgee.

About 11pm on Sunday the vehicle was swept off a causeway and into Cooyal Creek.

The driver, a 45-year-old man, and two male passengers - aged 43 and 26 - escaped and made their way to safety.

The 28-year-old woman did get out of the car, but was then swept away sparking a land, water and air search.

The woman's body was located on the riverbank about 9.50am on Monday.

"While she is yet to be formally identified, it is believed to be that of the missing 28-year-old woman," a NSW Police spokeswoman said.

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A report will be prepared for the information of the Coroner.

It comes following a rescue of an elderly couple and their dog in floodwaters at Moama on the NSW-Victorian border on Sunday afternoon.

The flooding emergency is far from over in south-east Australia, with more rain on the way across NSW and Victoria.

Here's how things are looking across the two states:

There are 122 flood warnings in place, including 20 emergency evacuation orders that include: Moree, Terry Hie Hie (south-east of Moree), Gunnedah, Mudgee, Narrandera and Moama.

During the past 24 hours there have been 37 flood rescues, 482 requests for help and more than 520 personnel working in flood zones.

There are 43 local government areas that are subject to a natural disaster declaration.

In Lismore, river levels are high and SES volunteers and Australian Defence Force personnel conducted doorknocks in the area overnight until 1am on Monday.

"The system that was expected to impact us last night deteriorated overnight and into the early hours of this morning," SES Lismore City Unit said.

A submerged vehicle was found in Swan Bay. There were no occupants in the vehicle and police will undertake checks to ensure its occupants are safe.

Many areas in the northern rivers have received at least 100mm of rain overnight, which has led to moderate flooding.

Areas on the mid north coast received 75-80mm in the 24 hours to 9am on Monday.

Later on Monday, heavy rain possible over the south coast, with rain also in the western districts and Riverina.

Severe weather warnings for heavy rain are still in place for the Riverina, Lower Western and Upper Western districts.

NSW Premier Dominic Perrottet said flood help was available and the government is "we want to make sure that no community is left behind".

Widespread rainfall has been recorded, with 10-30mm across western and northern Victoria and the Gippsland, and 100mm in 24 hours over the South Australian border in Renmark.

Victoria SES chief operations officer Tim Wiebusch said people near the Murray River, from Swan Hill to Mildura, should prepare for floods and pay attention to alerts from emergency services.

"Victoria is still very much in a flood emergency at this time," Mr Wiebush said.

Bureau of Meteorology senior meteorologist Kevin Parkyn said rain and thunderstorms are expected, but severe weather warning for heavy rainfall has now been lifted.

"We're still quite concerned that thunderstorm activity will develop," he said.

Storms could produce up to 60mm of rain and flash flooding.

"The combination of these local heavy falls and these widespread falls that's coming down from Queensland as part of this tropical air mass will put pressure on the river systems," Mr Parkyn said.

A flood watch for minor to moderate flooding is active for much of Victoria.

A separate low pressure system is moving down NSW coast towards Victoria which will bring rainfall into Gippsland.

Widespread rainfall is expected from Sunday onwards.

It is likely to be among the 10 wettest Octobers on record.