Residents have been ordered to evacuate ahead of major flooding as northern NSW is lashed by heavy rain caused by the remnants of ex-tropical cyclone Debbie clashing with a cold front.
The State Emergency Service advised on Thursday afternoon that people within the South Murwillumbah, Condong and Tumbulgum areas should leave.
"The NSW State Emergency Service is directing residents to evacuate immediately where safe transit exists and they are able to do so," the order issued about 4pm said.
"Do not delay your evacuation. Roads will be congested or closed. You could become trapped and need rescue."
The Bureau of Meteorology says major flooding is forecast along the Tweed River with levels predicted to be similar to 2001 and 2008 floods.
"Major flooding is forecast along the Tweed River at Murwillumbah late Thursday afternoon," the bureau said in a flood warning issued after 3pm.
"Further rises are possible with rainfall forecast overnight tonight."
Almost 400 millimetres of rain has fallen in just 24 hours over the Tweed River valley and there have been significant river level rises.
A severe weather warning has been issued for destructive winds, heavy rainfall, abnormally high tides and damaging surf along the coast north of Sydney and for the northeast of the state.
"Twenty-four-hour totals in excess of 200 millimetres are expected over the northern rivers district during Thursday and it is likely some locations will significantly exceed 350mm," the bureau warns.
It also says more than 100mm are possible over parts of the northern ranges and slopes and parts of the mid north coast on Thursday.
Watch: Cyclone Debbie's aftermath in Proserpine
