The Environment Agency issued a record number of flood alerts – more than 600, including four severe “danger to life” warnings – as more than a month’s worth of rain fell in 48 hours in some parts of the country.
Police forces declared major incidents in South Wales, Shropshire, Worcestershire and Herefordshire as rivers burst their banks and landslides blocked roads and trapped residents.
One of the worst-hit areas on Sunday was the village of Nantgarw, near Cardiff, which was left with entire streets underwater.
“I’ve never experienced anything like this before,” said Paul Mason, group manager of South Wales Fire and Rescue Service, which carried out hundreds of rescues of people and their pets.
“We started getting calls at 5am. The water was up to the window sills in some instances, so we sent a number of boats and crews down here, systematically going through each of the houses, knocking on doors, trying to prioritise individuals.
“This weather is unprecedented. It’s incredible, and it’s right throughout the South Wales Valleys. In my 31 years in the service this is the worst I’ve ever seen.”
Melanie Hughes, 38, said she was awoken by shouting and car alarms in the early hours and managed to get everybody safe.
“We were lucky,” she said. “But our cars, kitchen, furniture, it’s all gone. It’s going to be a couple of months of hard work, now. It was filthy, there was nothing to salvage.”
More than 1,000 homes were deluged by water in the Rhondda Cynon Taf area alone, prompting Pontypridd MP Alex Davies-Jones to launch a crowdfunding appeal. “Seeing the floods devastate our communities is truly heartbreaking,” she said.
A man in his sixties died after being pulled from the River Tawe near Swansea on Sunday morning but police said the death was not suspicious or linked to the bad weather.
The River Teme also burst its banks and flooded villages on the Shropshire and Worcestershire border. In Lindridge the fire and rescue service even had to rescue their own colleagues who had become stranded in a fire engine.
Dozens of roads and railways were also flooded after torrential downpours and high winds caused by the second storm in just over a week.
All train services between the southwest of England and Bristol, and between Southampton and Bournemouth, were cancelled.
Parts of the UK were also battered with winds of more than 80mph, with the highest measuring 91mph in Aberdaron in north Wales.
More than 150 flights were cancelled on Sunday morning due to the weather conditions. Video footage showed a passenger plane landing almost sideways at Heathrow airport while battling with powerful headwinds on Saturday.
However, the environment secretary George Eustice said he did not anticipate the government would declare a national emergency. “We are not expecting any more heavy rain until at least next weekend, so there will be some respite,” he said.
“It’s not a national emergency yet but it is certainly a local emergency in many of those areas affected.”
A yellow severe weather warning for wind remains in force for western and northern England until 11am on Monday. Gusts of up to 70mph are expected to bring further travel disruption.
“We are not out of the woods yet with wind,” said Met Office meteorologist Craig Snell. “We have also got to get all this water through the river system so even though the warnings from us may expire, flood warnings are likely to remain in force for the next 24 hours.”
Severe flood warnings remain in force for the rivers Neath and Taff in south Wales, as well as the River Teme further north.
The Met Office said a total of 156.2mm of rain fell at Crai Reservoir in Powys in the 48 hours from Friday to Sunday morning, compared to the monthly average for February of 111.1mm.
High river levels in York, West Midlands, Derbyshire, Nottinghamshire and southern England are expected to last until Wednesday, according to the latest forecast.
“Storm Dennis will continue to bring disruptive weather into early next week, and there are flood warnings in place across much of England,” said Environment Agency flood duty manager Caroline Douglass.
“We urge people to check the flood risk in their area and remain vigilant.”
Additional reporting by Press Associaton