Flash flooding has left parts of Aberystwyth under water as the Met Office issued thunderstorm warnings for most of the UK until Thursday.
The Environment Agency has said isolated flooding is possible across parts of England over the next few days due to heavy storms.
The Met Office warned that flash flooding could cause travel disruption and power cuts, but also cautioned about the risks caused by fast flowing or deep floodwater.
Images have shown vehicles struggling to make it through flooded streets in Aberystwyth, west Wales.
Councillor Ceredig Davies, who covers the Aberystwyth Central ward, told WalesOnline the area hasn’t seen a downpour like it in years.
He said: “There are a number of properties in town that have flooded towards the lower part of the town – and a number of high street shops have had water coming through.
“It was such a downpour.”
Most of the UK is covered by a Met Office yellow warning until Thursday meaning thunderstorms are likely.
The warning states there is a small chance homes and businesses could be flooded with damage to some buildings.
Thunderstorms are expected in the coming days after an intense period of hot weather where temperatures reached 34C at Herstmonceux in East Sussex on Sunday.
It was the fourth consecutive day the thermometers passed 30C in the south of England.
There is every chance hot weather will remain, with temperatures of up to 36C possible across the south coast at the beginning part of the week.
Bonnie Diamond, a meteorologist with the Met Office, said on Monday: “There is a pretty broad warning in place today, but there is another for central UK – the Midlands up to the North West of England to about Cumbria, and into Wales – which we are watching really closely.
“We are looking at the potential for some thunderstorms there from about 4pm to the early hours.
“It’s a worst-case scenario – a caution, really, for what could happen – but we are looking at a potential for 150mm of rain in three or four hours.
“Normally for August you’re looking at around 70mm for the month, so it’s potentially a lot of rain.
“To get that much it will take some areas seeing frequent thunderstorms, and not just passing through.”
Caroline Douglass, flood duty manager with the Environment Agency, said heavy thunderstorms this week “could lead to surface water and river flooding in some communities” into Tuesday morning.
She said: “Isolated flooding is also possible more widely across England today through until Thursday due to further heavy thunderstorms.”