The river hit 8.24m on Saturday morning, just shy of the predicted 8.3m peak by the Bureau of Meteorology (BoM).

The major flooding - levels above 7.90m - is expected to remain across town well into Sunday as the wall of water moves downstream, pushed by releases from Keepit Dam.

The State Emergency Service (SES) said it was watching the pulses in the river caused by the Keepit releases.

Water NSW has not said when the releases will finish, but is making controlled releases for Keepit Dam which topped 100 per cent.

The SES said the floodwaters had remained for more than 24 hours at the major flood level upstream of Gunnedah at Breeza, meaning it could take some time before the water moves past Gunnedah and recedes to minor and moderate flood levels.

A number of homes across Gunnedah have floodwaters through the properties but the SES said it would not know the full count until the major flooding recedes.

More than 1000 sandbags were used to protect homes, businesses and sporting facilities from the water.

Rain has also fallen across the town on Saturday, with smaller storms and showers passing through and delivering almost 4mm to the town's rain gauge.

The Kamilaroi Highway is shut between Gunnedah and Boggabri after the road went under water earlier on Saturday.

Motorists who need to travel between Gunnedah and Narrabri can use the Oxley Highway and Newell Highway via Coonabarabran instead. Live Traffic NSW said this will add about 90 minutes extra to the trip.

Further north through Wee Waa, the Kamilaroi Highway remains closed between Spring Plains Road at Narrabri and Doreen Lane at Merah North.

A number of roads across the Gunnedah, Liverpool Plains and Narrabri shires are closed to all traffic after being inundated by the flooding.

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A driver had to be rescued by the Gunnedah SES from a flooded and closed road overnight in Gunnedah.

"Please, if there is a road closed sign up, it means the road is closed. This is a genuine safety issue and we ask people not to drive around them, as we do not want to see any flood rescues in Gunnedah today," an SES spokesperson said.

"This will free up our volunteers to provide community support and also give us the chance to collect flood intelligence for our records, to continue to assist and inform the community.

"Also, we should continue to see pulses along the river today as the waterway continues to respond to the releases upstream from Keepit Dam."

The flooding is now headed for Boggabri, Narrabri and Wee Waa, which remained isolated and cut off by all roads in and out of the town.

Minor flooding is already occurring along the Namoi River at Boggabri and Narrabri, and last weekend's flood peak from Gunnedah peaked early Thursday in Wee Waa.

Wee Waa is expected to experience major flooding until at least Friday, the SES said.

Extra resources have been deployed to the area and essential food drops and pharmacy supplies have already been delivered to the town.

On Saturday, the SES said all grocery resupply orders needed to be placed through the IGA on Monday, Wednesday and Friday for Tuesday and Thursday deliveries.

The SES expects the Namoi River at Boggabri to peak near 7.80m on Sunday with minor flooding.

Gunnedah Road, Barbers Lagoon Road, Manilla Road, Maules Creek Road, Therribri Road and Bostons Street Bridge may all be affected by floodwater, authorities said.

The Narrabri Creek at Narrabri could reach about 5.70m during Monday. with minor flooding.

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