The hospital in the NSW town of Ballina has been evacuated, as the town braces for a "life threatening" one-in-500-year flood, while Sydney and surrounds prepare for up to 200mm of rain.
Northern NSW Local Health District said 55 patients were moved to Ballina's Xavier Catholic College with the help of NSW Police, NSW Ambulance and the SES last night.
A makeshift emergency department is being set up at at the college.
"The evacuation is taking place on the advice of the local Police Commander and out of an abundance of caution to protect the health and safety of patients and staff," NSW Health, said.
Earlier, forecasters warned of "a life-threatening event" heading for the town, after devastating Lismore and surrounds, further north, leaving one woman dead and many others awaiting rescue.
"This is a very serious situation and should be monitored closely as the water levels continue to rise," Northern Rivers SES, said in a statement.
Some houses are already under water around the town, with many people having to be evacuated by boat.
Cows and sheep were also rescued from the Richmond River.
Water levels are expected to top 2.5m in Ballina, with a map showing much of the town in the danger zone, and telling people to evacuate.
Meanwhile, people in low lying parts of the beachside town of Lennox Head, further north have also been told to get out, with a fresh evacuation order in place.
The town of Maclean, further south, is also among areas going under.
Essential Energy said still 20,000 remain without power on the NSW north coast.
Multiple road closures remain in the area.
Wild weather moves south
The weather bomb which has left nine dead in south east Queensland and northern NSW is moving south, with the Hunter Valley, South Coast and Sydney in line for flash flooding with 50mm -150mm of rain expected and up to 200mm possible in some spots.
The BoM warns of heavy rain, life threatening flooding and winds covering: Gosford, Sydney, Penrith, Parramatta, Wollongong, Nowra, Bowral, Campbelltown, Batemans Bay, Braidwood, Bega and Moruya Heads.
"A deepening low off the central coast of NSW is expected to drift south westward towards the coast overnight rapidly deepening in response to an amplifying upper trough and low and will continue on this track through Wednesday," it said.
"At this stage, the system is forecast to approach central and southeastern districts during Wednesday and overnight into Thursday, however, uncertainty exists on its exact timing and where the most significant impacts will occur.
Warragamba Dam is at 99 per cent capacity, and a spill could come today.
Residents around the Hawkesbury River, north of Sydney, which suffered floods last year, are also bracing for the weather.
Wednesday morning could see minor flooding, possibly rising by the evening to 7.9m near Windsor.
The nearby Colo River is also under an alert.
Minor flooding is likely along the Upper Nepean River at Menangle Bridge this morning, affecting the MacArthur areas of Menangle, Douglas Park
It could rise to 9.2m later.
Other alerts have been issued for the Georges River at Liverpool Bridge, which is likely to reach the minor flood level by 9am, according to the SES, with a similar level expected at Milperra Bridge.
Take note of orders, officials say
"Be very aware of where you are and what your danger is," Ms York told A Current Affair.
Yesterday in Sydney's North Epping a teenager had to be rescued from a rising steam by Toll Rescue Helicopter and Ambulance NSW urging people to stay out of rising waters.
Bushwalkers are being told to stay at home after a pair had to be rescued in the NSW Blue Mountains yesterday.
A 55-year-old man and a woman, aged 33, had to be rescued due to rising water on a walking track in Wentworth Falls- which they'd gone down despite it being closed.
They were winched to safety by Police Rescue and NSW Ambulance paramedics.
In Sydney's Inner West the SES has been going door to door in Marrickville, warning of possible of flash flooding.
People also waited hours for sandbags from Penrith to Beverly Hills to get their homes ready for the possible deluge.
BOM Weather warning
Water shortage in town
The northern NSW town of Mullumbimby is running out of water.
Officials have warned portable water, which was brought in after the water treatment plant was knocked out by floods, is "critically low" and will run out today.
"Staff are currently working on getting the plant up and running again but it will take at least 48 hours until we can treat the water so it is safe for drinking and restore the water supply," Byron Shire Council, said.
They urged people to conserve water, and hoped to bring in bottled water today.
Meanwhile a landslide has cut off the nearby village of Main Arm.
A pregnant woman was winched from a tinnie after crawling out the window to escape a flooded home, in one of several rescues carried out by the Land Rover LifeFlight Special Mission helicopter crew, in Northern NSW.
The specially trained rescue crew came to the aid of 19 people and a dog yesterday.
The SES has warned people could be cut off for days.
A woman in her 80s was found dead in a home in Lismore, the first victim of the floods in the state.
Eight people have lost their lives in Queensland's flood crisis.