A giant, out-of-control blaze has fuelled dangerous fire-generated thunderstorms as residents in northern NSW scramble to shelter from the inferno.

The fast-spreading Duck Creek Pilliga Forest bushfire was burning about 20 kilometres south of the town of Narrabri – home to more than 12,000 people – and a similar distance from Boggabri to the east on Tuesday morning.

The fire had burned through more than 110,000 hectares and authorities warned embers from the blaze were being blown well ahead of its front, causing a danger to homes.

Overnight it generated a thunderstorm from a pyro-cumulonimbus cloud system to the south-east, causing dangerous and erratic fire behaviour, the NSW Rural Fire Service said on Tuesday.

Residents of Baan Baa, Willala, Goolhi, Rocky Glen and Stannix Park were told their lives were at risk and it was too late to leave, and they should seek shelter and avoid being caught in the open in the fire’s path.

Narrabri Shire mayor Darrell Tiemens, who spent the night fighting the fire with other volunteers, said the blaze grew “very, very quickly” and had created its own weather system.

“Luckily, I don’t think we’ve had any homes lost yet – although we just don’t know,” he said.

Council staff and other workers had done 24-hour shifts to keep services online as the bushfire caused power outages along local roads, Tiemens said.

“Hopefully rain later this evening will bring a reprieve, it’s just very unpredictable,” he said.

The temperature was forecast to hit 36 degrees in Narrabri on Tuesday. However, showers and a possible thunderstorm were expected in the afternoon and night.

Evacuation centres have been set up at Narrabri and Gunnedah.

RFS spokesman Greg Allan said the bushfire had been fanned by northerly winds overnight and during the morning, pushing the blaze to the south.

“The fire is likely to stay at emergency warning level for some time,” he said.

It was unsafe for building-assessment teams to access the fireground and work out if any properties had been damaged or destroyed, Allan said.

Smoke from the fire on Monday could be seen across an area spanning hundreds of kilometres, including Tamworth, Walcha, Armidale and coastal communities near Port Macquarie.

There were 63 fires burning across the state on Tuesday morning, including 15 that were yet to be contained.

More than 450 firefighters and other personnel were working to control the blazes in easing conditions for the north of the state.

There are no total fire bans although there are high fire danger rating for the area from Sydney west to the Victorian border.

Temperatures in the mid-30s or above were forecast for Sydney, parts of the mid-north coast, and north-west and central-west slopes and plains on Tuesday

-AAP