Major flooding is expected in the Mungindi area on Wednesday, after the river level peaked on Tuesday.
The State Emergency Service (SES) update on Tuesday afternoon warned flood peaks from both the Macintyre River and the Weir River had arrived in Mungindi.
The Barwon River at Mungindi was expected to reach the major flood level, and the SES said flooding would continue on Wednesday.
The flood is not expected to burst the town's levee bank.
Mungindi has been cut off by surrounding floodwater for a few days, and the SES has been choppering in essential supplies twice-a-day.
The SES confirmed on Tuesday afternoon residents can now get to grocery shops and other essential stores in both Dirranbandi and St George in Queensland via the Carnarvon Highway.
"With road access confirmed to St George, the NSW SES will be reducing the resupply operations to the Mungindi township," a statement from the SES said.
"NSW SES will continue to provide and facilitate essential services from Moree daily such as pathology, water sampling, Australia Post, hospital and medical supplies, and support those isolated rural properties."
The Carnarvon Highway is still closed between Moree and Mungindi.
Major flooding is also expected at Mogil Mogil later in the week, and moderate to major flooding may develop at Collarenebri, Walgett and Brewarrina.