Video report by ITV News Calendar reporter Jon Hill
Rescuers reported seeing sheds and oil tanks floating down roads as "100 or more" homes in the Yorkshire Dales were deluged on Tuesday.
A bridge over Cogden Gill on Grinton Moor, which featured in the opening stage of the 2014 Tour de France and is due to be on the route of the prestigious UCI World Championships in September, was wrecked.
An ice cream parlour reported customers being injured in a freak hailstorm, and the site of a planned mountain biking festival was left devastated.
Steve Clough, of Swaledale Mountain Rescue, said: "The roads were a raging torrent and there were sheds and household oil tanks floating down them."
Mr Clough said his team spent more than eight hours searching properties in the area, rescuing about 10 people, but he added that North Yorkshire Fire and Rescue Service helped many more and estimated "100 or more" homes had been affected.
"Some homes had a metre of water in them – it was horrific," he said.
The fire service said it received around 115 calls to flooding incidents in Leyburn and Reeth on Tuesday evening.
Pictures and videos on social media showed widespread flooding across the Swaledale area in the Yorkshire Dales.
Roads resembled rivers, with many cars stranded, and fields were under water.
The Brymor Ice Cream parlour, near Masham, was caught in a freak hailstorm which left some customers with minor injuries.
The attraction posted on Facebook: "Our parlour suffered damage to the roof, power failures and some visitors suffered minor injuries.
"Our team of staff acted as quickly and professionally as possible to ensureall our visitors were made safe."
Preparations for next weekend's Ard Rock mountain biking festival were under way in Swaledale but the event has now been cancelled.
Soldiers from the 2nd Battalion of the Yorkshire Regiment, also known as the 2 Yorks, were carrying sandbags in the area around where the festival was due to take place in a bid to help the clean-up.
Farmer Raymond Caldert said: "I haven't seen anything like this.
"We had a storm here about 20 years ago, called Hurricane Charlie. I thinkthis has been worse."
He added: "The bridge has gone. There's quite a few bridges have gone."
Train passengers also faced disruption after a landslip between Carlisle andSkipton.
Malham Tarn, in the Yorkshire Dales, had 3.2in (82.2mm) of rain in 24 hours, the majority in the space of four hours. The monthly average in the area for this time of year is 3.5in (89mm).
The Met Office said storms could dump up to 1.6in (40mm) of rain in twohours in places on Wednesday.