Witnesses who rushed to help an injured man after lightning struck a tree on the main road through Dannevirke say they thought a bomb had gone off.

Staff at Property Brokers Dannevirke, which is directly across State Highway 2 from the tree, was one of the first on the scene when the man, thought to have been hitchhiking at the time, was injured in the strike during Wednesday's wild electrical storm.

Forked lightning and crashing thunder struck the Tararua town just before 3.20pm, accompanied by heavy rain.

Kerry Sutherland points out the damage to the tree. Photo / Leanne Warr

Manager Kerry Sutherland, who has lived in Dannevirke for about 45 years, said he had never seen a storm like it.

"The whole ground shook. I thought it was a bomb at first but you kind of knew it was different from sheet lightning," he said.

There was also a smell of ozone and smoke.

The injured man, thought by firefighters to have been hitchhiking at the time, had been seen seeking shelter from the storm under the tree but witnesses could not agree on whether he was struck by the lightning or just from the bark of the tree.

The man, who was travelling from the United Kingdom, was taken to hospital and had been released.

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Locals rushed to help the man injured after lightning struck the tree. Photo / Supplied

Two men from a local removal company were first on the scene and were able to provide blankets for the man.

A witness said the two men in the truck saw the lightning and the injured man fall to the ground.

Those who ran to help said the man was at first numb from what could have been shock and probable concussion but was fairly coherent and even cracking jokes.

Liam Webber was looking out the window at his work when he saw the lightning strike. Photo / Leanne Warr

Liam Webber, who works at Jon Telford Autos, said he was "scared out of my seat".

He'd been on a break and was looking out the window when the lightning hit.

He said there was a massive explosion and the tree caught on fire.

"I've never seen anything like it before."

Brianna Bonnington-Mudford, who recorded a video near the scene just minutes before the lightning strike said she'd been told by the driver of a truck that had passed through that he had felt the electric current go through him.

The storm lasted less than 30 minutes but required multiple fire callouts, including to the scene on Stanley Street at 3.19pm.

Sutherland said he had contacted the Tararua District Council as he was now concerned about damage to the tree which could be potentially dangerous.

- Leanne Warr, HBT