As the big wet continues on the NSW north and mid north coast, residents are being warned to prepare for worse to come.

While conditions had eased some, a severe weather warning highlighting heavy rain for the following 48 hours was issued by the Bureau of Meteorology on Monday afternoon.

'We are expecting the worst to come,' SES spokesperson Becky Gollings said.

'Rain is likely to pick up late Tuesday afternoon into the evening and push through until Wednesday morning.

'Tuesday is the day of greatest concern for us at the moment.'

Up to 200mm more rain could fall in parts of the Northern Rivers district over the following two days and some catchments may receive higher, the bureau said late Monday afternoon.

However motorists returning from long-weekend getaways were being urged to take extra caution, especially if travelling in the north and mid north coastal regions, with high tides and rain expected on Monday evening, Ms Gollings said.

The area has already been drenched with in excess of 150mm over the weekend.

Heavy rain and thunderstorms may lead to flash flooding in the Northern Rivers region and northern parts of the mid north coast.

SES crews have already carried out 600 flood rescues this year and they don't want that number to rise, Ms Gollings said.

Locations of concern include Lismore, Grafton, Coffs Harbour, Sawtell, Woolgoolga and Dorrigo, while there are also warnings for the Brunswick, Wilsons and Richmond rivers.

'Don't drive through floodwaters and weirs. Take it easy. It is better to actually be delayed than to risk your life and having to send somebody to rescue there,' Greg Murphy from the SES said.

The Rural Fire Service, Fire Rescue, local police and councils and the SES are preparing for emergencies and possible flooding in the coming days.

As the big wet continues on the NSW north and mid north coast, residents are being warned to prepare for worse to come.

While conditions had eased some, a severe weather warning highlighting heavy rain for the following 48 hours was issued by the Bureau of Meteorology on Monday afternoon.

'We are expecting the worst to come,' SES spokesperson Becky Gollings said.

'Rain is likely to pick up late Tuesday afternoon into the evening and push through until Wednesday morning.

'Tuesday is the day of greatest concern for us at the moment.'

Up to 200mm more rain could fall in parts of the Northern Rivers district over the following two days and some catchments may receive higher, the bureau said late Monday afternoon.

However motorists returning from long-weekend getaways were being urged to take extra caution, especially if travelling in the north and mid north coastal regions, with high tides and rain expected on Monday evening, Ms Gollings said.

The area has already been drenched with in excess of 150mm over the weekend.

Heavy rain and thunderstorms may lead to flash flooding in the Northern Rivers region and northern parts of the mid north coast.

SES crews have already carried out 600 flood rescues this year and they don't want that number to rise, Ms Gollings said.

Locations of concern include Lismore, Grafton, Coffs Harbour, Sawtell, Woolgoolga and Dorrigo, while there are also warnings for the Brunswick, Wilsons and Richmond rivers.

'Don't drive through floodwaters and weirs. Take it easy. It is better to actually be delayed than to risk your life and having to send somebody to rescue there,' Greg Murphy from the SES said.

The Rural Fire Service, Fire Rescue, local police and councils and the SES are preparing for emergencies and possible flooding in the coming days.

AAP