NSW's Northern Rivers region is being battered by a "natural disaster of unprecedented proportions" as floodwaters in Lismore hit record levels, emergency services minister Steph Cooke says.
There are now 17 evacuation orders and 21 warnings in place, affecting 62,000 people, with residents in Lismore working to rescue stranded neighbours.
Ms Cooke said emergency services were focused on saving lives and conditions were expected to get worse.
Lismore's levee was breached early this morning and the level of the Wilsons River rose to 14.37m - more than 2m higher than the previous benchmark set in 1954.
"This is entirely unprecedented for this region. So, for those people who have lived here, or lived in that wonderful part of the world, for many, many years, we need you to please be on alert now more than ever," Ms Cooke said.
"These conditions are different to anything you will have experienced before."
The State Emergency Service (SES) said its crews had carried out 512 flood rescues across NSW in the past 24 hours.
It has had 1011 call outs, with 408 of those in Lismore.
Premier Dominic Perrottet said scenes in Lismore were "incredibly distressing" and the severe weather had been "worse than expected".
"If you are in one of those areas where there is an evacuation warning in place, please begin planning and preparing for evacuation," he said.
"And if you can leave, and it is safe to do so, please, please leave."
Mr Perrottet said the government and emergency services were doing everything they could to get to stranded people as soon as possible.
He urged residents to follow the advice of the SES and not to take risks, which could have tragic consequences.
Ms Cooke said conditions had hampered attempts to get Rural Fire Service aircraft in the air, but three Australian Defence Force (ADF) aircraft were en route to the region.
There are 200 ADF personal on the ground in Lismore assisting with sandbagging efforts and logistics.
The SES received 374 calls for help in 30 minutes this morning, and at one stage asked people with boats to help rescue stranded residents — however, that call-to-arms was cancelled when the situation became too dangerous.
Despite this, local social media pages are full of offers to help with rescues, and many more pleas for assistance.
Lismore resident Katie Davies and her three children were among those forced on their roofs to avoid the "rapidly rising" water.
"We're not even the worst," Ms Davies said.
"We have an elderly couple stuck in their roof cavity, they're banging on the roof asking for help and we can't help them.
"It's rising rapidly, they need help desperately, every house on our street there's people perched on their roof."
Rescue efforts across the NSW North Coast are being hampered with many SES personnel isolated in their homes.
Flood intelligence officer with Lismore SES Ed Bennett said it was difficult to comprehend the amount of water inundating the area.
"We tend to think that when there is a new flood record it might be a little bit above the highest known flood, [but] to be nearly a metre and a half above what was already incredibly high is just hard to comprehend," he said.
The BoM is forecasting up to 200mm of rain to fall in Lismore today.
Evacuation orders issued
While a flood evacuation warning is in place for the entire Northern Rivers, people several specific locations have been ordered to leave their homes.
Lismore Mayor Steve Krieg said the situation in his city was "diabolical".
"A lot of people stayed on and a lot of people felt that, given previous floods in Lismore, that their houses, at least their top level of their houses would be a safe place, and now even their top floors are underwater," he said.
"I have been fielding calls from very distressed residents who are sitting on rooftops trying to get help. It is diabolical."
Emergency services have warned residents in Grafton they may need to evacuate this afternoon, with the Clarence River already dangerously high.
"We are warning pretty much all of Grafton … especially if you have had flooding in the past, we're suggesting now is the time to start lifting your furniture and stock if you're a business owner," Dave Rankin from the SES said.
"There's no sign of this storm cell lacking in intensity in the next 24 hours and it's coming South.
"So people in the Clarence Valley and Mid North Coast must be very aware there is a lot of rain coming over the next 24 hours."
The BoM's Gabrielle Woodhouse said there was widespread rain across the Clarence Valley.
"Rainfall rates are generally around the 10-20 millimetre mark per hour but we're also seeing areas of much more intense rainfall up towards the 40-70 mm per hour range," she said.
Man missing
Police were last night forced to suspend the search for a man, believed to be missing in floodwaters in Lismore's CBD.
Police say they saw and heard the man calling for help yesterday afternoon, but lost sight of him.
The SES's incident controller Steve Patterson said the man may have been washed down a drain.
Police entered the water and searched for a man but couldn't find him. Efforts were suspended last night after it was deemed too dangerous to continue.
Meanwhile, the SES has directed people living below the Rocky Creek Dam, 25km north of Lismore, to evacuate immediately as "uncontrolled water" spills over.
The SES is warning residents that if they stay they will be "trapped without power, water and other essential services and it may be too dangerous to rescue you".
There are widespread power outages across the region with the Lismore SES headquarters going dark earlier this morning.
Staff had to move operations to higher ground at the Lismore Heights Bowling Club, after the headquarters came under threat of inundation.
Several evacuation centres have been set up across locations in Tweed Heads, Murwillumbah and Lismore, for those who are unable to stay with family or friends or find alternative accommodation.
