Lightning struck a large Watford home this morning before a massive fire "erupted" through the roof.

Four engines rushed to what is believed to be a six-bed property in Cassiobury Drive at 5.24am and found residents lining the street in the pouring rain.

No one was injured, Herts Fire and Rescue confirmed, though crews had to tackle a "substantial fire" and stopped it spreading to nearby properties.

A neighbour told the Watford Observer they heard a "massive bang" and thought it was very close to their home, before realising next door had smoke billowing from the roof.

Watford Observer: The fire ripped through the home's roof.The fire ripped through the home's roof. (Image: Submitted)

Recalling watching on outside, they said: "Then all of a sudden the thing burst into flames. The flames shot through the centre of the roof.

"As luck would have it the fire engine turned up, got a hose on it and controlled it. Eventually a cherry picker came and they got on top to get closer to it. All a bit dramatic."

He continued: "I just spoke to the people's daughter and she said it's destroyed the whole top floor of the house, everything burnt and damaged.

"As luck would have it, it's a bit of a self-contained area (Cassiobury Drive) and it didn't spread further down."

Watford Observer: The fire service outside the house with the roof damaged.The fire service outside the house with the roof damaged. (Image: Submitted)

Watford Observer: Fire crews at the scene.Fire crews at the scene. (Image: Submitted)

Although the strike woke him and his wife immediately, he said his neighbour didn't realise what had happened until the police knocked on their door and told them their roof was on fire.

"We were counting ourselves lucky as it's like 10 metres away from a tall chimney so it could easily have been my house," he added.

It happened amid a Met Office yellow weather warning for thunderstorms.

Herts Fire and Rescue's watch commander from the Watford station, Mark Woodward, said: “Our crews were faced with a fairly substantial fire in the roof. We sent in two teams in breathing apparatus to attack the fire from inside the building, and they were able to successfully stop the fire before it spread too far.

Watford Observer: Fire crews at the scene.Fire crews at the scene. (Image: Submitted)

"Fortunately a passerby had alerted the residents to the fire and everyone was safely out of the building when we arrived at the scene.

"From talking to the residents and looking at the pattern of the fire, we believe the fire was started by a lightning strike.”

Watford Observer: The damaged roof.The damaged roof. (Image: Submitted)

Watford Observer: The damaged roof.The damaged roof. (Image: Submitted)