Two men died and dozens of people had to be rescued from their homes on Tuesday night as more than a month's worth of rain fell in a few hours, causing widespread flooding.
Among the worst hit areas were south-west Scotland, north-west England and south Wales where roads were closed, rail services were disrupted and the emergency services were stretched to the limit.
In west Wales, a police officer was killed when his car crashed in treacherous driving conditions on the A40 near Haverfordwest. In the Scottish Borders, where particularly heavy storms forced a severe flood warning of "serious danger to life and property" being issued across the Teviot Valley , a 76-year-old lorry driver from Newcastle was killed when his vehicle overturned on the A68 near Ancrum.
At least five people were rescued in Hawick after part of the town was deluged by floodwater 4ft deep. "There were cars floating about on the high street and there was a car actually through one of the windows of a local shop," said local businessman David Blair, who had been shocked at the sudden devastation.
A spokeswoman for Lothian and Borders Fire and Rescue Service said they had been "inundated" with calls for help.
"Several elderly people were rescued after they were trapped in the upper floors of their addresses," she said.
The rain also caused disruption to road and rail travel as landslides closed the A708, two miles east of Moffat, and the B709 between Eskdalemuir and Langholm in Dumfries and Galloway.
On the railways, flooding forced the closure of the west coast main line between Cumbria and Glasgow, forcing passengers travelling between England and Scotland to switch to GNER services on the east coast main line.
In Edinburgh, part of a wall collapsed on to a line that carries freight trains and, although there were no injuries, all traffic had to be diverted.
By yesterday morning, there were 15 severe flood warnings in place across Scotland and six more in Wales and Cumbria.
A total of 63mm fell in Eskdalemuir in just 12 hours on Tuesday between 6am and 6pm, while 100mm - nearly 4ins - fell in Milford Haven, south Wales, between 6pm on Monday and 6pm on Tuesday. In Keswick, Cumbria, 82mm (3.2ins) of rain fell in 24 hours.
In Carlisle, which suffered serious flooding in January, some families who had only just moved back to their homes were forced to leave once again. Chief Inspector Kevin McGilloway, of Cumbria Police, said residents of Warwick Road in Carlisle, one of the worst-affected areas earlier this year, had been flooded again.
"You can imagine what it was like for people who have just moved back into their houses," he said. "It's those at the top end of Warwick Road , nearest to the M6, who have been hit again."
There were also reports of flood damage in Wales from Whitland and Cardigan to Haverfordwest, Tenby and Pembroke Dock.
Mid and West Wales Fire Brigade said they had received at least 120 separate calls reporting flooding in Pembrokeshire alone.
In north Wales up to 20 properties at Groeslon, near Caernarfon were flooded and the A487 was closed at Llanwnda.
"Many areas in Wales, north-west England and Scotland saw up to the average monthly rainfall in a 24-hour period," said a spokesman for the PA Weather Centre. "The general outlook for today onwards is much better conditions just about everywhere. That's through the weekend and perhaps into next week as well."
The floods followed a warning from the Environment Agency that too many people were ignoring flood risks and that many households were alarmingly complacent about the threat. The agency said 5 million people in 2 million properties in England and Wales lived in flood risk areas, but research indicated that 41 per cent of these households were unaware of the danger.Reuse content