A man in his 80s died after his car was submerged in flood-waters amid a deluge of rain across the West Midlands.
Rescuers had to swim 50m to reach the motorist, whose vehicle was "completely underwater" in Walsall.
In Birmingham, more than a month's rainfall hit parts of the city in an hour on Sunday. Areas of Northamptonshire were also flooded.
Weather warnings have been issued for Monday, while the South East could see the hottest day of the year so far.
Emergency workers were called to Lichfield Road in the Rushall area of Walsall shortly after 02:00 BST on Monday morning.
'Two inches of breathing space'
West Midlands Ambulance Service (WMAS) paramedic Peter Bowles was at the scene and tweeted that firefighters and ambulance staff had to swim 50m to reach the man.
Four paramedics went into the flood-water and carried out life support, WMAS said.
He was taken to hospital where he died a short time later. His family has been informed.
Drainage engineer Ben Lees had rescued another man from the same road on his way home earlier on Sunday.
He said there was about 2in of breathing space in the car when he swam to it and dragged the man out.
The Far Cotton area of Northampton was severely flooded along with major roads in the county including the M1 and A45.
The Environment Agency has issued multiple flood warnings and alerts covering much of central England.
Despite the flood warnings, Met Office meteorologist Craig Snell said temperatures could hit highs of 28C or 29C in the South East.
He said: "It all depends how much cloud develops. There's a chance we could see the warmest day of the year."
In Birmingham, one major route in the city was rendered impassable by water up to 5ft (1.5m) deep.
The Met Office said a site at Winterbourne, in Edgbaston, recorded 58mm of rainfall in just one hour on Sunday afternoon, and 81mm in a 12-hour period.
The monthly average for the West Midlands region in May is 55mm, Mr Snell said.
But he said the torrential rain had been "very localised", pointing out that another site 10 miles away at Coleshill recorded just 3mm of rain in 12 hours.
BBC journalist Rebecca Woods said she had driven past a large number of flooded and closed roads in the Harborne and Selly Oak areas.
She said she had seen flooded houses and it had taken her 90 minutes to drive about five miles.
We’re issuing multiple flood warnings in the #Birmingham area as smaller rivers react rapidly to torrential rain. Situation compounded by severe surface water flooding in some places.— Dave Throup (@DaveThroupEA) May 27, 2018
Take extreme care if in the area.
Flood warning updates here https://t.co/lay6cxAT3K pic.twitter.com/7jai0DQFk7
In Sir John's Road, Selly Park, homes flooded and cars were under water, while wheelie bins floated down the road.
Resident Stu Dunigan said water was above waist height, almost submerging cars on the street.
It is the second time in two years the street has flooded. More than 100 homes were flooded June 2016 causing some residents to leave their houses.
Some had only recently returned before Sunday's floods.
Trevor Thomas, who lives in Kings Heath, had to leave his home when it was flooded with six inches of water.
Mr Thomas, 51, is severely disabled and had to be taken to stay with his 73-year-old mother, Pat Thomas, at her home in Kings Norton.
She said the house was not suitable for her son and they both had to sleep on the sofa as she could not get him upstairs to bed.
Jacqui Kennedy from Birmingham City Council said the operation to clear up debris and repair roads was under way.
Police said some roads in Birmingham were still affected by flooding and advised drivers not to ignore road closure signs.
In Pelsall, Matthew Swain thanked his "lovely neighbours" who helped his elderly grandparents by sweeping the water out of their house in Fordbrook Lane while their own homes were also flooded.
"They left their own houses and came to my grandparents' rescue," he said. "I'm so grateful and thankful to them all."
Northampton council leader Jonathan Nunn and councillor James Hill visited St Leonard's Road in Far Cotton to speak people affected by flooding.
Mr Nunn said: "We want to know exactly what happened and work out ways to prevent it happening again."
Part of the M1 and A45 in the county were under three feet of water and drivers were trying to pass through the floods.
The A5 was closed in both directions in the border area of Leicestershire, Warwickshire and Northamptonshire, between the junctions of the A426 at Churchover and the A428 near the Dirft rail terminal to the east of Rugby.
Warwickshire Fire and Rescue Service (WFRS) said it had also been "extremely busy" dealing with flooding calls on Sunday evening.