The Bureau of Meteorology has issued an initial Flood Watch for the Wilsons and Richmond Rivers for late Sunday into Monday as the expected rainfall increases.

As a precaution, the NSW SES advises people in the Northern Rivers to STAY INFORMED about predicted slowly rising minor flooding on the Wilsons River and Richmond River in low lying areas, causeways and culverts.

The forecast thunderstorms that never eventuated Saturday, look like being a day late as a trough lingers near the coast until Tuesday or Wednesday, with severe thunderstorms and locally heavy rainfall possible. This rainfall may cause minor flooding across parts of the Northern Rivers.

Catchments are currently relatively wet across the Flood Watch area. Minor flooding is possible from overnight Sunday and into Monday. Flood Classes (minor, moderate, major) are only defined for catchments where the Bureau provides a flood warning service.

The Bureau has cancelled the severe thunderstorm warning and issued a Severe Weather Warning for Heavy Rainfall.

"Persistent showers and thunderstorms with heavy rainfall are expected to trigger a coastal trough during Sunday and Monday, with further support from an upper trough sitting to the southwest.

"HEAVY RAINFALL which may lead to FLASH FLOODING is forecast for the Northern Rivers and parts of the Mid North Coast and Northern Tablelands districts during Sunday and Monday. Three to six-hourly rainfall totals between 80 and 160 mm are possible, with isolated 24-hourly totals exceeding 250 mm possible.

"Heavy falls will be associated with shower and thunderstorm activity, which is likely to be somewhat hit-and-miss in nature across the warning area. These conditions are expected to continue during Monday, though rainfall may ease in the Mid North Coast by Monday morning.

"Localised intense rainfall is possible under areas of persistent heavy thunderstorms. Separate severe thunderstorm warnings may be issued to highlight areas of intense falls if they are detected."

Locations which may be affected include Lismore, Grafton, Coffs Harbour, Woolgoolga, Sawtell and Dorrigo.

110 mm recorded in Sawtell in the 2 hours to 1:15 pm.

100 mm recorded in Coffs Harbour in the 2 hours to 1:00 pm.

The State Emergency Service advises that people should:

* Don't drive, ride or walk through flood water.

* Keep clear of creeks and storm drains.

* If you are trapped by flash flooding, seek refuge in the highest available place and ring 000 if you need rescue.

* Be aware that run-off from rainfall in fire-affected areas may behave differently and be more rapid. It may also contain debris such as ash, soil, trees and rocks.

* After bushfires, heavy rain and the loss of foliage can make the ground soft and heavy, leading to a greater chance of landslides.

* Stay vigilant and monitor conditions. Note that the landscape may have changed following bushfires.

* For emergency help in floods and storms, ring your local SES Unit on 132 500.

The next Severe Weather Warning will be issued by 5:00 pm AEDT Sunday.

• What you need to do:
• If you have a Home and/or Business Emergency Plan, review it now. Otherwise, have a conversation and plan for what you will do and take with you if you need to evacuate. Consider the consequences of road and bridge closures and water over roads and make alternate arrangements for work, children, and travel.
• Obey all signs about road closures and instructions from emergency services.
• Never drive, walk, ride through, play or swim in flood water - it is dangerous, toxic, and may void your car insurance. If it's flooded, forget it. Fines may apply.
• Avoid storm drains and pipes, ditches, ravines, creeks, and rivers.
• People in areas likely to be impacted by flooding should raise their assets, including waste and chemical containers above expected flood heights.
• Share this information with family, friends, and neighbours and help others prepare where possible.
• If you are likely to be isolated due to flooding, stock up on essential items now. Farmers should consider moving pumps and farm equipment to higher ground. Companion animals and livestock should be relocated to higher ground that will not become an island.

For more information:

Listen to your local ABC radio station which can be found at reception.abc.net.au. ABC North Coast,

Follow us on social media @NSWSES or visit our website at www.ses.nsw.gov.au. Learn about your risk at www.ses.nsw.gov.au/knowyourrisk/

Check the latest weather, warnings, rainfall and river heights at www.bom.gov.au/nsw/. Check road closures at livetraffic.com.au or 132 701 or your local Council.

Check out The Bureau's Weather App and Weather Radar, including warnings on the Lismore App Weather & Travel.

For emergency help in floods, storms and tsunamis, call the NSW State Emergency Service on 132 500. In life threatening situations, call Triple Zero (000) immediately.