More thunderstorms are set to hit southern parts of the UK as the hot weather brings with it torrential downpours.
Holidaymakers enjoying the long weekend and those off for half-term have been warned of the risk of flash floods and sudden worsening of visibility amid heavy rainfall.
Southern England and much of Wales is covered by a yellow weather warning, with the thunderstorms looking likely to continue into Tuesday.
One elderly man lost his life in the early hours of Monday when his vehicle became submerged in Walsall, and multiple rescues had to be carried out from cars, buses and homes on Sunday, the West Midlands Fire and Rescue Service technical rescue unit said.
While further thunderstorms are forecast for parts of Wales and England the rainfall is unlikely to be as intense as Sunday's, the Met Office said, predicting up to 30mm rainfall in the space of an hour in affected areas.
Although temperatures had been tipped to rise to the highest of the year so far, late-clearing cloud kept the mercury lower than expected, forecaster Greg Dewhurst said.
"The cloud cover took longer to burn back this morning so it's just kept things a bit cooler and just hasn't had that full amount of sunshine to heat everywhere up," he said.
Thorney Island in West Sussex was the warmest recorded spot by late afternoon, peaking at 25.8C, a few degrees shy of the April high of 29.1c in central London.
A combination of warm, unstable air and light winds has sparked the thunderstorms, Mr Dewhurst said.
Dozens of flood alerts remained in place on Monday for the Midlands and some southern parts of England.
The Environment Agency has warned people not to drive through floodwater, reminding people that just 30cm can move a car.
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.
Staffordshire and West Midlands Fire Control received more than 900 weather-related calls, with crews attending 100 incidents on Sunday evening.
Birmingham City Council, which said it could not yet put a figure on how many properties have been affected, has advised that while flood water is subsiding in the area, people should take care and beware of debris.
A clean-up operation is under way with extra street cleaning crews working to clear rubbish from affected areas.
Carol Holt, Environment Agency flood duty manager, said: "Further heavy showers in some parts over the remainder of this bank holiday weekend carry a risk of further localised flooding.
She added: "Our thoughts are with those who have been affected by the flooding this weekend and our teams are working with those communities who have experienced flooding.
"We are continuing to check and operate defences and we are supporting local authorities in responding to surface-water flooding."
Emergency services were called to the Walsall incident shortly after 2am to find two vehicles in the flooded Lichfield Road in Rushall.
The victim, aged in his 80s, was taken to hospital where he later died, but a second person found in the water was unhurt, West Midlands Ambulance Service said.
Forecaster Greg Dewhurst said: "I would say pretty much anywhere across England and Wales could see some thunderstorms but they won't be as intense as they were yesterday.
"They could still give some torrential downpours, some localised flooding is still possible, some local hail as well and lightning but they shouldn't be quite as intense as they were yesterday."
Scotland and Northern Ireland enjoyed a warm, dry Monday with highs of 25C and 23C respectively.