The Bureau of Meteorology forecasts that severe thunderstorms are possible north of Coffs Harbour, bringing moderate and locally heavy rainfall that could lead to flash flooding.
There is a risk of super cell thunderstorms, which could bring damaging winds exceeding 90 km/h and large hail.
If the forecast rainfall occurs, minor flooding is possible in the Northern Rivers catchments from late Friday including Tweed and Rous Rivers, Brunswick River and Marshall Creek, Wilsons River and Richmond River.
NSW SES North Eastern Zone Commander Rhys Gloury said the main hazards we are likely to see with this rain will be flash flooding.
"We could see water cover roads quite quickly and would like to remind the community to steer clear of floodwaters," Chief Superintendent Gloury said.
"If you come across a flooded road, turn around and find an alternative route."
Chief Superintendent Gloury said NSW SES crews are prepared to respond to any impacts of the severe weather but asked communities to be prepared too.
"People can prepare their homes by clearing gutters and downpipes before the weather hits, trimming overhanging branches and tying down loose items," he said.
Residents and visitors are urged to download the Hazards Near Me app and set up a watch zone to stay across the latest warnings and advice.
"We have a number of people visiting the area for sporting events and ask those travelling to set up a watch zone so you are alerted with local warnings and information," Chief Superintendent Gloury said.
Conditions are expected to ease by Monday, with light showers forecast.
If you need assistance during storms or floods, call the NSW SES on 132 500. In a life-threatening emergency, always call triple zero (000).
