The Bureau of Meteorology has issued a severe thunderstorm warning for damaging winds and heavy rainfall for Lismore and parts of the Northern Rivers.

A southerly change is moving through the northeast of the state this afternoon and evening, where a humid and unstable airmass is in place. Thunderstorms are possible ahead of and with this change, and some may be severe with damaging winds and heavy rainfall.

The severe thunderstorms may lead to flash flooding for Lismore, Ballina, Evans Head, Yamba and Grafton.

Separate Flood Watches are current BoM issues Minor Flood Watch for Wilsons and Richmond Rivers.

Safety advice

The State Emergency Service advises that people should:

* Park your car under secure cover and away from trees, powerlines and drains.

* Secure or put away loose items around your house, yard and balcony.

* Keep at least 8 metres away from fallen power lines or objects that may be energised, such as fences.

* Report fallen power lines to either Ausgrid (131 388), Endeavour Energy (131 003), Essential Energy (132 080) or Evoenergy (131 093) as shown on your power bill.

* Keep clear of creeks and storm drains.

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

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

* Stay indoors away from windows, and keep children and pets indoors as well.

For emergency help in flood and storms, ring the SES on 132 500.

Stay updated on the Hazards Near Me NSW app or the ACT ESA website (https://esa.act.gov.au).

Check https://www.bom.gov.au/weather-and-climate/warnings-and-alerts.

The next warning is due to be issued by 7:55 pm.