The giant, out-of-control Duck Creek Pilliga Forest bushfire has fuelled the creation of its own thunderstorm.
The raging blaze increased overnight, and as of the early afternoon of Tuesday, December 19, had burned more than 112,245 hectares.
The increase was a result of the fire taking a 30-kilometre run to the south towards Rocky Glen and Stannix Park.
Narrabri Fire Control Centre public information officer, Kate Carter, told the Leader, the extreme conditions and unexpected winds had resulted in the fire creating it's own weather conditions.
The weather phenomenon, known as pyro-cumulonimbus, is when the heat builds up from the bushfire causing the fire to rise and cool and grow storm clouds.
"On days when the weather is hot and humid and primed to generate storms," said Bureau of Meteorology meteorologist Belinda House.
"Bushfires could act as the trigger to start thunderstorms, in turn creating their own weather around bushfire sites."
The thunderstorm can result in the fire behaving in an erratic and dangerous way.
Ms House said the Pilliga region was expecting showers and thunderstorms this afternoon and into the evening.
"There is a continued risk that the fire will itself generate storm activity," she said.
Smoke from the fires burning in the Pilliga has been experienced across the NSW North West, into the Hunter region and down into the Greater Sydney area.
The smoke is expected to clear later this evening when forecast southerly winds move through the state.
The NSW Rural Fire Service upgraded the fire status to Emergency during the evening of Monday, December 18, with residents at Baan Baa, Willala, Goolhi, Rocky Glen and Stannix Park advised to seek shelter.
Residents located at Bohena Creek, between McCanns Road, Perimeter Road, Tomlinson Lane, and Newell Highway were also included in this advice.
The fire's alert level was downgraded to Watch and Act on Tuesday, December 19 at about 2.30pm.
The Newell Highway remains closed to traffic in both directions.
The NSW Rural Fire Service has set up an evacuation centre at The Crossing Theatre in Narrabri and the Gunnedah PCYC.