Rain has brought relief for those battling a major bushfire in north-west New South Wales, which has already burned through more than 112,000 hectares.

The fast-spreading Duck Creek Pilliga Forest blaze was burning about 17 kilometres south of the town of Narrabri and 21 kilometres west of Boggabri on Tuesday evening.

Emergency services issued a renewed warning for the out of control blaze, before downgrading it roughly an hour later to a watch and act.

“Due to significant amounts of rain now falling across the fireground, the alert level has been downgraded,” the Rural Fire Service said.

“Residents in the vicinity should continue to monitor conditions.”

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Thunderstorms that hit the area in the early afternoon made for erratic fire behaviour, with residents near McCanns Rd, Jacks Creek and Bohena Creek told it was too late to leave and to seek shelter, at 6.30pm.

Shane Allan, whose parents own Bohena Pet Motel on the Newell Highway south of Narrabri, said the family had evacuated the animals and was preparing to fight any fires that broke out on the property.

Allan told AAP the rains came as a major relief as trees along the property boundary began to ignite.

“It was just starting to bust through our border coming past our fence, and then the storm hit,” he said.

“Mother nature came to our rescue.

“You couldn’t have planned it any better.”

A severe thunderstorm warning was issued for the area on Tuesday afternoon, with potentially damaging winds, hail and heavy rainfall.

Smoke from the blaze was being carried as far as the Hunter and Sydney regions, affecting air quality ahead of a forecast southerly change.

Earlier in the day the fire was downgraded from emergency level to a watch and act about 1pm as crews had success controlling pockets when it entered farmland from the Pilliga.

Overnight the blaze generated a thunderstorm from a pyro-cumulonimbus cloud system.

Residents of Baan Baa, Willala, Goolhi, Rocky Glen and Stannix Park were told on Tuesday morning that their lives were at risk and it was too late to leave, before the warning was downgraded.

Narrabri Shire Mayor Darrell Tiemens, who spent the night fighting the fire with other volunteers, said the blaze grew “very, very quickly”.

“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 been doing 24-hour shifts to keep services online as the bushfire caused power outages along many local roads, Tiemens said.

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

The temperature hit 35 degrees Celsius in Narrabri on Tuesday, however showers and a possible thunderstorm were expected in the afternoon and evening.

Evacuation centres have been set up at both 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.

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

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

No total fire bans applied, but a high fire danger rating was in place for an area stretching from Sydney’s west to the Victorian border.

Temperatures reached into the mid-30s for Sydney, parts of the mid-north coast, and north-west and central-west slopes and plains.

-AAP