Severe thunderstorms with almost a month's worth of rain, frequent lightning strikes and hail are set to batter Britain.
The Met Office has issued a 'danger to life' warning for heavy rain and thunderstorms which are set to herald the end of the late August heatwave.
Up to 60mm of rain - almost a month's worth for some places - could fall in just two or three hours as forecasters warn of possible flooding, power cuts and travel disruption.
The yellow warning for thunderstorms stretches almost the entire eastern side of the country from Scotland to London, with parts of the North West of England and Midlands included.
It comes after Britons basked in 33C heat during a record-breaking Bank Holiday weekend.
The heatwave is continuing on Tuesday with temperatures due to peak in the low 30s, but stormy conditions will move in from the afternoon.
The Met Office said: "Although some places will miss them, heavy showers and thunderstorms will break out in some areas this afternoon.
"Where thunderstorms do occur, torrential rain and frequent lightning is expected as well as a chance of gusty winds and hail here and there.
"A few spots could see as much as 30mm rain in an hour and 40 to 60mm rain in two or three hours."
A high of 33.2C at Heathrow Airport made it the hottest August Bank Holiday Monday on record.
Met Office meteorologist Craig Snell said: "The heatwave is going to continue for some of us for another day with temperatures reaching around 33C, but also across the UK we are also starting to see a transition with some places seeing cloud and fresher air.
"This cloud will start to move up across Devon and Cornwall and through this evening it will come across northern and central parts of the UK."
The Met Office said the risk of heavy rain and thunderstorms will increase as the week goes on.
Mr Snell added: "Temperatures will be staying close to the high 20s but the rain and thunderstorms will start moving eastward."
The cloud and risk of thunderstorms will then draw up across Northern Ireland and will bring cloud to more parts of the country.
Mr Snell said: "For some of us we have still got some hot weather to come but that transition over the next 48 hours will come with a risk of heavy rain and thunderstorms."
During Monday's record-breaking temperatures, Bala in Snowdonia National Park was the warmest place in Wales, with a top temperature of 25.5C.
Fyvie Castle in Aberdeenshire, Scotland, reached 25C and Helen's Bay in Northern Ireland saw the mercury rise to 21.9C.
The previous best August Bank Holiday temperatures before this weekend were 31.5C at Heathrow in 2001, 27.3C in Velindre, Powys, in Wales, and 27C in Knockareven, Co Fermanagh, both in 2003, and 26.7C in Aviemore, Scotland, in 1984.
Met Office five-day weather forecast
Tuesday
Outbreaks of rain in Northern Ireland and western Scotland.
Isolated thundery showers over Wales and the southwest of England will slowly fade.
Thunderstorms developing over parts of northern, eastern and central England, and southeastern Scotland later.
Hot in the southeast.
Tuesday night
Evening thunderstorms over north and east England and east Scotland soon clearing.
Rain in the far west and northwest will become more widespread in western areas.
Warm in the southeast.
Wednesday
Rain in the west moves slowly eastwards to lie across southeastern Scotland, north England, Wales and southwest England by late afternoon.
Brighter with showers elsewhere.
Less hot in the southeast.
Thursday to Saturday
Dry for many Thursday, but wet and windy weather arrives in the northwest later.
Wet and windy conditions in the northwest on Friday spread southeastwards on Saturday with winds easing.
