NSW floods: Bleak warning as Byron Bay, Lismore go under water

Northern NSW is facing another flooding emergency just weeks after much of the state was hit with a once in a generation flood event.

The popular tourist town of Byron Bay has seen its main streets submerged on Wednesday morning, while residents in Lismore have been urged to evacuate for the second time this week as the city's flood levee height was exceeded mid-morning, with floodwaters and mud once again spilling into the CBD.

Speaking at an emergency press conference, acting premier Paul Toole said no one could have predicted the immense amount of rain seen in parts of the state in the last 24 hours.

"When you have a look at the rainfall, no one could have predicted some of the amounts we have seen," he said.

"We've seen 430mm of rain land within (some of) these communities.

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

Flooding sirens in Lismore malfunction

Frustration in Lismore had grown after an evacuation order was cancelled half an hour after being issued on Tuesday. The order to evacuate was then re-issued late Tuesday night.

SES evacuation orders now apply to thousands in the region with the state's emergency services announcing that flooding sirens in Lismore were malfunctioning.

"EVERYONE MUST GET OUT OF THE CBD IMMEDIATELY," the NSW SES tweeted shortly after 10am.

Lismore City centre residents along with those in surrounding Lismore Basin, East Lismore and Girards Hill were urged early Wednesday to leave immediately.

Meanwhile flash flooding hit Byron Bay and Ballina overnight, with residents and local journalists taking to social media to share pictures of main streets under water.

Further south, heavy falls and thunderstorms which could lead to flash floods with the possibility of dangerous and life-threatening conditions is forecast for parts of the Mid North Coast and Northern Tablelands.

Six evacuation orders are in place across NSW for areas including the Lismore CBD, Lismore Basin, low-lying areas of East Lismore, North Lismore and Girards Hill, Riverside Caravan Park Coraki, Tumbulgum, low-lying parts of Kyogle, parts of South Lismore, and Bellinger River Tourist Park on the north coast.

Six-hour rainfall totals between 80mm and 140mm are possible, while up to 300mm may fall over mountainous coastal areas, the Bureau of Meteorology says.

Locations in the warning zone include Grafton, Coffs Harbour, Port Macquarie, Taree and Dorrigo.

Bleak warning for weeks ahead

Despite the acting NSW premier insisting the latest rain dump was unpredictable, he warned the state could see more in the coming weeks.

"I want to indicate that we are still expecting a very wet autumn. Over the coming months, we may see the situation coming back again," Mr Toole told reporters.

"April is expected to be quite wet in many parts of the state."

"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)."

That sombre warning was echoed by the state's emergency minister Steph Cooke.

"We know that this wet weather is likely to continue for some time right through April and potentially beyond that," she said.

with AAP

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