The town of Wee Waa could be cut off by flooding as severe thunderstorms lash the north-west of the state.
It comes as towns in the area have already been hit by flooding including Gunnedah.
Residents in Wee Waa could become isolated for up to 10 days, New England NSW State Emergency Service (SES) said.
“The Namoi River at Wee Waa is likely to exceed the moderate flood level (6.40m) during Thursday and may reach the major flood level (6.70m) during Thursday evening,” it wrote.
“It is currently at 6.32m and rising slowly.”
Heavy rain and storms have lashed most of the state today.
A severe weather warning is in place for Broken Hill as well as most of southern NSW, the Bureau of Meteorology (BoM) said.
“This rainfall may cause new and renewed flooding across NSW inland rivers and the Hunter River, many of which have been impacted by recent flooding,” the BoM said.