Thunderstorms and heavy showers are set to hit much of the UK today with up to 60mm of rain falling in some places in just three hours.
The Met Office has issued a yellow weather warning for thunderstorms covering vast swathes of England and forecasters have warned of potential disruption.
The thunderstorm warning runs until 6am on Wednesday, while a separate more serious amber thunderstorm warning in Scotland is in place until midnight on Wednesday, with forecasters saying "heavy thundery showers will bring some travel disruption and some localised flooding".
The Met Office said up to 60mm of rain could fall in some areas, as heavy showers and thunderstorms develop into Wales and northern and central England.
In a statement, it said: "These will last well into the night across north Wales and north-west England in particular where they could be prolonged in places.
"20 to 30mm of rain is possible in around one or two hours, and a few places could see around 60mm in three to six hours. Lightning and hail may pose additional hazards in a few locations."
It comes after torrential rain flooded parts of London and the South on Sunday.
London saw nearly a month's worth of rain fall with homes, roads and Tube stations flooded, while a flooded hospital cancelled all surgery and outpatient appointments on Monday due to heavy rain.
The Mayor of London, Sadiq Khan, said recent flooding in the capital shows "the dangers of climate change are now moving closer to home".
He said the emergency services and local councils had hundreds of calls regarding the weather on Sunday afternoon and evening.
He added: "The serious flash flooding in London over the last two weekends will have caused major concern and anxiety for many Londoners and it shows that the dangers of climate change are now moving closer to home.
"Despite having limited powers in the area, it remains a key priority for myself and London's council leaders that more is done to urgently tackle flooding and the other impacts of climate change.
"This is why I have brought together all of the key partners to see what more can be done, including the water companies who have to address the localised issues with infrastructure that may exacerbate the impact of flooding."
The wettest part of the country on Sunday was St James's Park in London, where 41.8mm of rain fell.
The average rainfall for July in London is 45mm, meaning nearly a month's worth of rain fell in one 24-hour period.
The daily rainfall value of 41.8mm recorded at St James's Park is that weather station's second-wettest July day on record.
The recently re-elected mayor added: "I continue to lobby the government to devolve more funding and powers to local leaders to enable us to deal with both flooding and the wider impacts of climate change.
"COP26 this year provides an opportunity for the government to show global leadership and give us the powers and resources we need to take even bolder action on climate change."