MORE rain and damaging winds are expected to lash the north of NSW this afternoon and tonight, with the Bureau of Meteorology issuing another severe weather warning for the Northern Rivers and Mid North Coast regions.

Bureau of Meteorology hazard preparedness and response manager NSW Agata Imielska said some very heavy rainfall has battered the north of the state from Friday but also overnight, with more on the way.

"For the Northern Rivers and Mid North Coast we will see a return of the heavy rainfall, so currently we are seeing relatively calm conditions but very important to be aware we are expecting very heavy rainfall to start again for the Northern Rivers and Mid North Coast areas with widespread totals of 100 to 200mm expected for those regions," she said.

"We also have very strong damaging winds across the northern coast, which is coinciding with king tides, which means we have a greater risk of coastal erosion and coastal inundation which is yet another reason to be mindful of the damaging surf conditions."

A trough over the Coral Sea is deepening offshore of the southern Queensland coast and as this trough deepens, a low pressure system is expected to develop and move towards the southern Queensland coast today and into Monday, before drifting south and weakening on Tuesday. This system is likely to bring significant rainfall, strong winds and large waves to the northern half of the coast until Tuesday.

River flooding for Mid North Coast and Northern Rivers is expected as a result with river levels expected to rise further from Monday and Tuesday.

High water levels due to spring tides are also forecast over the next few days, which adds to the risk of flooding in lower tidal areas.

A severe weather warning for heavy rainfall, which may lead to flash flooding, has been issued for the Mid North Coast and Northern Rivers.

Minor to moderate flood warnings have been issued for the Tweed and Bellinger Rivers and a minor flood warning has been issued for the Brunswick River and Marshalls Creek.

National Flood Services Manager Justin Robinson said flooding could be expected in the Clarence Valley and Coffs Coast regions.

"The Clarence River at Grafton, we're expecting some minor flooding is possible there, and with the Orara River at Coutts Crossing and Glenreagh we're expecting even moderate flooding for those communities," he said.

"Also for the Coffs Coast that had severe flooding at Sawtell, and for Coffs Harbour and those communities we're expecting the potential for some minor flooding.

"These are dynamic weather systems, and you should always expect the unexpected, and people should keep aware of the BOM's updates."

NSW State Emergency Service Commissioner Carlene York said the SES have had 700 calls for assistance, with 200 of them coming last night.

Commissioner York said additional SES crews have been deployed to the Northern Rivers region to assist with preparations and evacuations if necessary.

"The weather is going to be quite heavy over the next few hours with the effects of flooding in a number of areas, so it's not a time to take a chance and drive through flood waters," Commissioner York said.

"It does put yourself in danger as well as my SES volunteers that need to go out to the call.

"With the rain there's been a large amount of strong winds as well so our crews have been particularly busy in relation to reports of roof damage and leaking in houses."

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