A family has made a narrow escape as fire consumed their 10-bedroom home after it burst into flames during a wild storm north-west of Sydney.

Locals say a freak lightning strike may have sparked the huge inferno that completely ravaged the rural house in Glenorie on Wednesday night.

The blaze broke out about 7.30pm. It took 70 firefighters several hours to extinguish the flames, helped by a storm later in the night that delivered some rain.

Crews were still on the scene at Cattai Ridge Road about midnight.

Footage released by the NSW Rural Fire Service shows bright orange flames consuming sections of the roof and licking the night sky.

Thick smoke can be seen billowing from the one-storey building about 44 kilometres north-west of the Sydney CBD.

Matthew Lloyd, from the NSW RFS, said the sprawling home’s roof collapsed as crews were working and the fire was burning “quite hot”.

“It was a fairly significant fire that extended throughout the roof cavity,” he told the Nine Network.

“Unfortunately, despite the good work … it’s probably a total loss.”

The family of seven made a narrow escape and scrambled to safety without injury as locals in the tight-knit Hills District raced to help.

RFS, Fire and Rescue NSW, NSW Police Force and NSW Ambulance crews were all on scene.

Detectives and specialist fire investigators will look into the tragedy and may consider the possibility of a lightning strike as the cause.