The Bureau of Meteorology says thunderstorms are likely to produce heavy rains that may lead to dangerous and life-threatening flash flooding in Scone, Armidale, Tamworth, Gunnedah, Moree and Narrabri.
Showers and storms are also forecast for the Sydney area, due to intensify in the coming days.
A car gets stuck in floodwaters in Lismore, NSW.(Nine)
Flood-affected communities will begin a mammoth clean up this morning, as waters recede and reveal the damage.
In low-lying areas, including Lismore, flood waters remain over some roads. The town saw 92mm of rainfall in just two hours with a flood warning still in place for the Wilsons River.