The latest evacuation orders have been issued for Moree as a new major flood peak looms on the Mehi River, a tributary of the Gwydir River, threatening to surpass a 10.87m high mark recorded 67 years ago.
In all, there are 120 flood warnings current around NSW, 20 of them at emergency level.
The state's SES says it conducted 31 rescues and responded to almost 400 requests for help in the 24 hours to 9am on Sunday.
A man in his 30s died in a suspected drowning on Saturday at West Ballina, on the far north coast, while two men stranded in vehicles in the Southern Tablelands centre of Yass were rescued overnight.
Authorities say renewed thunderstorms have impacted multiple flood-affected communities along swollen rivers.
Most are in areas surrounding Moree, Gunnedah and the neighbouring village of Carroll on the northern Namoi River, the Riverina town of Narrandera on the Murrumbidgee and Moama on the Murray River.
"We are seeing more rainfall come through this morning, which will lead to more water movement and fill rivers and flooding," the SES said.
Incident controller Tom Jory said in a statement on Saturday the current predictions, while not as severe as earlier this year, meant low lying areas were still likely to be impacted.
The Bureau of Meteorology expects heavy rain over the state's northeast from Sunday morning, affecting Lismore, Grafton, Casino, Kyogle, Yamba and Maclean.
Falls of up to 150mm in six hours were possible in some areas.
Emergency Services Minister Steph Cooke says large parts of the state, including the inland and west, are in for a "difficult few days".
Emergency services and volunteers are currently handing out 30,000 sandbags a day.
"We are quite literally sandbagging the state," Ms Cooke said on Saturday.
Two hundred Australian Defence Force personnel have been deployed in Dubbo, Moree and the Northern Rivers, with two additional ADF helicopters ready for night rescues.
Specialist swift-water rescue crews have also been dispatched to the flood-threatened north while others are in place on the Macquarie River, at Dubbo.
The 12 local government areas added to the state's natural disaster declaration list are Albury, Berrigan, Carrathool, Cobar, Federation, Griffith, Hay, Leeton, Murray River, Murrumbidgee, Narrandera and Wagga Wagga.
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