Emergency services have carried out more than 100 rooftop rescues at Eugowra in Central West NSW, as thousands more are rescued or evacuated amid serious flash flooding across the state's west.
Several towns recorded upwards of 80 millimetres of rain and some locations reported up to 120mm yesterday and overnight, overwhelming already swollen rivers and dams that will cause renewed major flooding in the coming days.
The NSW State Emergency Service (SES) said in the past 24 hours there have been 855 calls for assistance including 204 flood rescues with 140 of those in Eugowra itself.
"This means with a population of 700, more than one in five [Eugowra] residents have been rescued in the last few hours by either helicopter or by boat," NSW Emergency Services Minister Steph Cooke said.
"This is a very serious situation, not just in Eugowra but in many places particularly along the Lachlan River.
"The ground is so saturated that all it takes is one heavy downpour to cause the type of life-threatening flash flooding that we have experienced overnight, and into today."
Twelve helicopters are working on flood rescue and supply operations, and 12 flood rescue operators are being dispatched from New Zealand to arrive in Sydney tonight before being deployed to Parkes tomorrow.
Seventeen emergency orders are in place in the state, including due to major flooding of the Murray River in the south, urging people to evacuate or move to higher ground.
In the Central West, emergency warnings are in place for parts of Cowra, Gooloogong, Canowindra, Derriwong and Eugowra.
Forbes is being told to evacuate before 9am Tuesday morning ahead of renewed record flooding.
Deputy Commissioner Sean Kearns said Eugowra was experiencing flash flooding not seen before.
"We already have at least about 300 people at the Eugowra showground who have evacuated to an evacuation centre there," he said.
An Australian Defence Force helicopter had earlier been dispatched to Molong to rescue people trapped in floodwater or needing medical help, floodwaters there have since receded and the emergency warning has been downgraded, advising people to avoid the area.
Fire and Rescue NSW (FRNSW) said its crews had also helped to rescue people stranded in roof-high floodwaters, inlcuding a couple from the top floor of a motel, while the NSW Rural Fire Service said it had rescued people from rooftops and others clinging to trees.
FRNSW said the floodwaters were so strong they smashed shop windows and knocked out the back wall of a supermarket.
Forbes had its highest daily rain total on record with 118mm and Orange, near Molong, had 89mm.
Some residents reported receiving more than 100mm in their rain gauges within hours at Molong.
"With those storms, over a million lightning strikes were recorded across much of the state," Steven Bernasconi from the Bureau of Meteorology (BOM) said.
"Of those million, 150,000 recorded as reaching ground from cloud to ground."
Molong resident Jill Englert said she was awoken at 2am by the sound of howling winds and pouring rain.
"It was just torrential, bucketing down, it was amazing," Ms Englert said.
"The recreation ground is a swimming pool and the railway lines are all under."
More than 1,500 residents in Molong, Cudal, Canowindra, Toogong are without power.
Record dam spill and renewed major flooding
Significant inflows into the Wyangla Dam on the Lachlan River caused spills to peak this afternoon at a record rate of 230,000 megalitres a day and could drop further later today.
That is well above flows of up to 125,000ML seen earlier this month, ahead of near record flooding downstream at Forbes, and more than the previous record of 205,000ML set in 1990.
Water NSW said in the first 11 days of November, even before yesterday's rain event, more than a third of the dam's capacity had already flowed into it.
"The upstream catchment is saturated, so inflows from the last rain event are still running in when you're trying to make space in the dam ready for the next rain event," Tony Webber from Water NSW said.
"In normal circumstances that next rain event might be three or four weeks away. Well, increasingly and acutely so in September and October, the next rain event is three or four days away, so it really is a challenging time for Wyangala."
Mr Bernasconi said Bathurst on the Macquarie River was preparing for its worst flood on record, with levels expected to reach up to 7 metres, above the previous record height of 6.7 metres in 1998.
"It will move fast and flow for this location which is making difficult to stay on top of the rises, it is forecast to reach 7 metres sometime this afternoon," he said.
Bathurst Council is currently working to close low points of the levee system.
The Lachlan River is expected to peak at Cowra and Nanami overnight and tomorrow, with major flooding.
Forbes is bracing for yet another major flood event with a peak of 10.8 metres possible on Thursday, similar to its worst flood on record.
Major flooding is already occurring further downstream at Condobolin with renewed rises possible from Tuesday.
The BOM said the next rain event affecting inland NSW was likely to develop over the weekend.
