Volunteers were on the ground inspecting properties as the Namoi River slowly subsides after major flooding on Sunday.

The river was hovering at about 7.91m at 4pm on Sunday and still above the major flood level.

Several areas remain isolated and the SES said its crews are conducting inspections and welfare checks "at properties where it is safe to access".

The Namoi peaked at 8.16m about 5.45am on Sunday inundating several streets and a number of homes.

"Our hardworking local volunteers have been active in the community undertaking inspections and doing welfare checks," an SES spokesperson said.

The spokesperson said more properties could have been hit but a full assessment could take some time because of the water levels and ability to get to cut off areas.

The SES said a number of teams have been on the ground responding to callouts and surveying water levels, even when "their own properties were at risk of flooding".

SES crews from out of area including Armidale were deployed to back up the volunteers on the ground.

The Oxley Highway reopened between Gunnedah and Carroll on Sunday afternoon but the Kamilaroi Highway remained shut late on Sunday between Narrabri and Wee Waa.

The Kamilaroi was also closed between Narrabri and Boggabri, and Boggabri and Gunnedah on Sunday because of flooding.

The Bureau of Meteorology - which is responsible for flood predictions - said the Namoi River peaked at Wee Waa at Glencoe at 6.86m on Sunday morning causing major flooding.

The peak hit at about 9.30am, isolating much of the area and the SES warned Wee Waa could remain isolated into Tuesday, depending on water levels.

The Namoi is expected to hit 7.70m on Monday with minor flooding in Boggabri, while the Narrabri Creek at Narrabri is likely to pass the minor flood level on Tuesday morning.

Dozens of roads across the Gunnedah and Narrabri shires were still closed late on Sunday after going under over the weekend.

THE NAMOI River is slowly starting to fall in Gunnedah after major flooding hit the town on Sunday morning.

Four homes were inundated in the town by Sunday morning, with the SES warning there may be even more flooding to come.

The river, which snakes through town, reached 8.16m at about 5.45 am on Sunday, just below the revised flood peak of 8.20m.

Several streets have been inundated across the town as well as sporting fields and paddocks.

The State Emergency Service (SES) has spent the morning doorknocking properties surrounded by floodwaters, and inspecting any damage.

At 1pm, it was sitting at 7.97m, still above the major level.

Acting SES deputy zone commander Craig Ronan said the water level would likely subside very slowly and the service doesn't expect the river to recede to below minor flooding levels before Monday afternoon.

"There's so much water in the system," he said.

"The ground is totally saturated, the dam's are full. This is the effects of La Nina, that was declared last week.

"We're going to see a wet summer and spring, this is going to be a common pattern over the coming weeks and moments."

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Authorities are watching Wee Waa closer after the Namoi River hit 6.85m at Glencoe earlier on Sunday.

Major flooding is expected to inundate low-lying areas around the town for Sunday and into the week.

The Oxley Highway remains closed between Carroll and Gunnedah due to flooding. Motorists can detour via the Kamilaroi Highway and Werris Creek Road through Quirindi to travel between Gunnedah and Tamworth.

The Kamilaroi Highway between Narrabri and Spring Plains Road is also closed due to flooding. Motorists can use the Newell Highway and Gwydir Highway via Moree to travel between Narrabri and Walgett.

Superintendent Ronan said Gunnedah will likely gets its fourth flood of 2022 as early as Thursday this week.

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Heavy forecast rain on Tuesday and Wednesday and an already-waterlogged environment will likely create even heavier flooding later this week, he predicted.

"People need to be aware. This rain could continue right through summer and spring. This might not be the only flood we see, or next week, there might be more," he said.

"We want people to be aware so the SES can do its role properly. We need people to be aware and resilient and understanding that this is so unprecedented, this weather. Catchments are sopping wet. Any rain is just going to produce runoff from now on, causing flooding."

If you need the assistance of the NSW SES, please call us 132 500.

AUTHORITIES have warned more homes and businesses in Gunnedah will be hit by floodwaters as a rising Namoi River passed its earlier predicted flood peak.

The Bureau of Meteorology (BoM) now predicts the flood peak will be 8.20m in the town on Sunday morning, potentially flooding more homes and properties.

Earlier predictions saw the flood peak revised to 7.90, but that was passed overnight on Saturday.

The Namoi was hovering at 8.1m about 5am on Sunday.

Authorities said they had to revise the flood height "substantially upwards" after floodwaters from the Peel and Mooki rivers saw more water inundate the system than previously thought.

Volunteers spent the night doorknocking homes at risk of being undated, and more homes and businesses will be contacted on Sunday morning, the State Emergency Service (SES) said.

The SES said based on the modelling it now predicts homes and businesses on the following streets could be inundated by floodwaters:

The SES said based on the current predictions water starts to encroach on the Woolshed Reserve, the Donnelly Playing Fields and the western end of Maitland Street near Benevolent Park.

"Access to Gunnedah airport from Gunnedah is impeded. The airport may close due to water covering the runway," an SES spokesperson said.

"Low-lying areas along the Namoi River including sporting fields, the tennis courts and racecourse may become impacted by floodwater."

The SES said it would continue to provide updates throughout the day.

"Please remember the NSW SES does not make flood predictions, like the community, we are now responding to the consequences as they continue to change," an SES spokesperson said.

"Please be nice to our volunteers this morning, they are locals too."

Wee Waa is already experiencing major flooding at the Glencoe area.

Dozens of roads are closed throughout the Gunnedah and Narrabri shires as floodwaters swallow thoroughfares.

The Namoi River at Wee Waa's Glencoe gauge could reach the major flood level of 6.90 on Sunday morning.

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The Namoi River at Boggabri may reach the minor flood level of 7.70m on Sunday morning.

The SES said renewed rises are likely along the Narrabri Creek and the river level at Narrabri is likely to pass the minor flood level of 4.90m on Sunday night. The BoM expected it could reach 5.50m on Monday with minor flooding.

Authorities again pleaded with motorists not to drive through floodwaters.

"We have already undertaken flood rescues this weekend. Our volunteers will be busy enough without having to rescue drivers who ignore road closed signs and stupidly drive through floodwater," an SES spokesperson said.

"Low-lying areas along the Namoi River may become impacted by floodwater."

On Saturday, the Oxley Highway was closed between Carroll and Gunnedah, and the Kamilaroi Highway was shut between Narrabri and Wee Waa.

Moderate flooding hit Tamworth on Friday afternoon after the Peel River peaked at 5.48m.

Floodwaters from the Peel River combined with the outflows from Keepit Dam and a flood peak from the Mooki River are behind the major flooding predictions for downstream, the BoM said on Saturday.

The SES said minor flooding is likely along the Namoi River at Boggabri, Narrabri, Bugilbone and Goangra in the coming days.

If you need the assistance of the NSW SES, please call us 132 500.

More to come.

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