The city of Lismore had its flood levee breached for the second time in weeks on Wednesday, as the Wilsons River peaked above 10.65 metres, with flood waters and mud spilling into the city centre.

“When you have a look at the rainfall, no one could have predicted some of the amounts we have seen,” NSW Acting Premier Paul Toole said.

“Four weeks ago these communities were impacted … no one could have predicted that we would be back here again.”

The acting premier said renewed flooding had come just as many people were returning to their homes and businesses.

The areas suffering the most impact were Lismore, Ballina, Byron, Coraki and Woodburn, he said.

Mr Toole said harsh, wet conditions were expected to continue, with a very wet April in prospect.

“We may be in this situation, coming back in a week’s time,” he said. “When you have a look at the ground it is saturated.

“You only have to see a small amount of rainfall landing in these areas (for further flooding).”

Flood Recovery Minister Steph Cooke said the state had faced many natural disasters over recent years.

“Whether it’s droughts or bushfires, and now floods,” she said.

“We know this wet weather is likely to continue for quite some time, right throughout April and potentially beyond that.

“I know for many of you it must feel that this flooding emergency will never end, but I can assure you that there is light at the end of the tunnel.”

Lismore Mayor Steve Krieg told AAP he had heard reports the Wilsons River had begun to tip over the top of the levee shortly before confirmation arrived from the Bureau of Meteorology.

“Everyone’s exhausted,” he said. “Evacuation orders started at four o’clock yesterday afternoon and then got cancelled before the phones started ringing again.

“(People are) running on no sleep at the moment.

“It’s hard to put into words. You’re feeling angry as well because the messaging hasn’t been what it should have been.”

Mr Krieg said most people in the area had lost the bulk of their valuables in the first inundation.

“The hardest thing for these people is they have spent weeks and weeks cleaning and getting rid of all the flood mud, sanitising and addressing the mould issue.

“Now you’ve got to virtually start all of that process from the start again.”

A small but intense low off the coast of Evans Head produced intense thunderstorms and remarkably heavy rainfall on Tuesday night, Dean Narramore from the Bureau of Meteorology said.

Communities from Evans Head to Byron Bay were hit with 200 to 300mm of rain within a few hours, causing significant and destructive flash-flooding, Mr Narramore said.

Numerous rivers in the Lismore area are experiencing major flooding, including the Wilsons – which continues to rise after breaking its levee on Wednesday morning.

In Coffs Harbour, Dorrigo and Bellingen, falls between 200 and 300mm were recorded overnight and major flooding is also occurring on the Bellinger River.

The NSW SES has undertaken more than 40 flood rescues in the last 24 hours, many of which were for people attempting to drive through flood waters, NSW SES Acting Commissioner Daniel Austin said.

“We ask for people not to drive through flood waters and to stay away from these environments,” he said.

Some 12 evacuation orders are in place across NSW, with an additional six issued on Wednesday morning.

The new orders are for Urunga CBD and Bellinger Keys, East Bellingen, Coraki and New Italy, Broadwater, Wardell and Cabbage Tree Island, and Newry Island.