An out-of-the-blue weather bomb that washed out roads and caused widespread flooding and property damage in Featherston was the worst torrential downpour a resident of 80 years has ever seen.

The heavens opened for about three hours on Sunday afternoon, wreaking havoc on the township and rural areas as the sun continued to shine in neighbouring Greytown and Martinborough.

The worst-hit area appeared to be Underhill Rd and Bucks Rd, where an entire two-lane road washed out, with a nearby resident's rain gauge measuring 100mm of rainfall in just two hours.

A section of Bucks Rd washed out in a weather bomb that hit Featherston on Sunday afternoon. Photo / Hayley Gastmeier
A section of Bucks Rd washed out in a weather bomb that hit Featherston on Sunday afternoon. Photo / Hayley Gastmeier

In town, houses were flooded and many residential roads were under water as the infrastructure failed to cope with the torrent of water pouring off the Remutaka Hill and surrounding ranges.

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Pat Kelly said he battled to get his "scared" cattle to move along Underhill Rd as heavy rain pummelled down between 4pm and 7pm.

"I've lived here 80 years and it was just a bloody weather bomb – I have never seen rain like it, never ever."

A 10m length of road dropped out on Bucks Rd, and a slip further up the hill meant freedom campers at Tararua Forest Park have been temporarily stranded.

The storm was so localised, a young family from Bucks Rd said they could see blue sky out the window a couple of hundred metres away, even though serious flooding was happening all around them.

"It was like someone just turned the shower on only this area," Jirayu Brennan said.

Her husband, David, negotiated the nearby slip to check on the stranded campers, who he said were in high spirits.

Dylan Bennett standing in his former paddock, that is now deep in metal. Photo / Hayley Gastmeier
Dylan Bennett standing in his former paddock, that is now deep in metal. Photo / Hayley Gastmeier

Dylan Bennett lives on the corner of Bucks Rd and Underhill Rd with his wife and baby son.

Silty water gushed through their house, ruining the carpets, and what was once a green paddock out the back of their large shed is now covered in a mound of large rocks.

He said the water level was waist-high when he was forced to move his digger to higher ground to save the motor.

"I just spent thousands grading my driveway to the shed and it's all gone. Rocks are now over my head where green paddock was."

On Monday morning, he was in knee-deep mud fishing out fence batons that had been ripped out and washed to the other side of his large section.

It would take Bennett weeks to sort out the mess.

"It'll be one day at a time, I think," he said.

Those who had the means to help rallied together with their machines to help out neighbours hit worst by the storm. Photo / Pete Monk
Those who had the means to help rallied together with their machines to help out neighbours hit worst by the storm. Photo / Pete Monk

Bucks Rd resident Lucy Harper said 100mm of rain fell in a short time and what was once a "pathetic stream" was now the size of a wide road.

"After about an hour [of rain] we were like, 'Wow, this is quite a storm' . . . it sounded like continuous thunder but it was actually huge rocks in the stream moving."

Derek Moore said there was "no life lost" on his farm but the landscape had changed considerably, with trees brought down and rocks and slush everywhere.

"One paddock is about 2m higher than it used to be … [and] I can't even recognise my gully now."

South Wairarapa Mayor Viv Napier, who was out talking to affected residents on Monday morning, said the weather event was "out of the box" and the council would assess whether any measures needed to be taken with the town's infrastructure.

The sewerage system had held up well. South Wairarapa District Council roading manager Tim Langley said the "high-intensity, short-term storm event" created flooding in unexpected areas, with new water courses scouring out a lot of fresh gravel and rock.