Parts of the UK will experience heavy downpours on Bank Holiday Monday - hours after temperatures exceeded 20C in what is likely the hottest day of the year.
The heavy rainfall will sweep eastwards and is significant enough for four flood alerts to already be put in place by the Environment Agency.
River Thame and Chalgrove Brook in Oxfordshire, River Rhee in Bedfordshire, Hertfordshire and Cambridgeshire, and Lower Frome and its tributaries in Somerset are subject to warnings.
Met Office has issued a yellow weather warning of thunderstorms across Northern Ireland from midday tomorrow to 9pm.
Rainfall will be heaviest in the south and west of the UK, and will turn to drizzle in the afternoon across London and the southeast.
The forecast is stark contrast to today's glorious sunshine and temperatures of above 20C for most of the country.
Mirror Online has broken down the forecast for each of the UK's countries and regions.
North of England
Temperatures will drop somewhat across Yorkshire tomorrow and rain will fall, heavily in the morning.
It could become thundery in the early evening, BBC forecasters believe, but will turn to drizzle by around 11pm.
As it won't be particularly windy, any drizzle will linger and cloud will remain all day across most of North of England.
Northwest England
The heaviest rain in Northwest England will likely fall at around 7am and linger for several hours.
Temperatures will struggle to exceed 13C, even when the rain abates at around 4pm.
It'll be particularly blustery in the morning, especially in and around Merseyside.
But the evening - before the approximate 8.50pm sunset - should be fairly pleasant across the region.
Northeast England
Following drizzle across the region in the morning, the Northeast of England will experience rather cloudy, dull skies throughout Bank Holiday Monday.
It'll be fairly warm once the rain abates at around 3pm with temperatures of 16C predicted in and around Newcastle.
Any lingering drizzle will move eastwards across the North Sea on Monday evening and into Tuesday morning.
West Midlands
Most of the West Midlands will experience heavy rain and a moderate breeze from around 10am tomorrow.
The rain, which will be fairly steady, should stop by around 5pm, forecasters say.
Temperatures will linger around the 12C mark, significantly cooler than today's balmy conditions.
Winds will be at the strongest - around 13mph - throughout the morning.
East Midlands
Likewise, towns and cities in the East Midlands will experience heavy precipitation tomorrow. It'll be the heaviest around lunchtime, BBC weather forecasters reckon.
It'll also be blustery in the afternoon, with wind speeds expected to hit 12mph at times.
Rain moves eastwards through the patch, and will largely vanish by around 7pm. It'll then remain cloudy throughout the night.
South of England
Rain will be heaviest in the South of England tomorrow night. Drizzle will blight Bank Holiday Monday daytime, and it'll be quite windy in the afternoon.
Gusts of around 13mph will be experienced in the region, forecasters say.
Temperatures will struggle to exceed 13C across the patch, it is understood.
Southwest England
It'll steadily rain across Southwest of England tomorrow, and it'll be windy in the morning with gusts of 13mph expected.
The drizzle won't abate until around 10pm, with cloudy spells inbetween any showers.
The heaviest rain will fall at around 4pm, forecasters predict.
London and the Southeast
The best of the weather - albeit largely still unsettled- will be seen in the capital and its surrounding areas tomorrow.
Temperatures should hit 15C in London, and it'll remain dry until at least 4pm.
Showers are forecast in the evening, though, and these could become heavy by around 7pm, particularly in Kent.
Winds will be lighter than elsewhere, especially in the morning.
East of England
It'll be cloudy and somewhat cold in the east of the country tomorrow.
Like in and around London, it should be quite dry but temperatures may dip to just 10C in rural parts.
Rain will arrive from the west at around 7pm but it should be fairly light and abate to drizzle later in the evening.
Winds will be strong in the afternoon, especially along the coast.
Scotland
It'll be a mixed bag across Scotland tomorrow. While it'll be very wet across most of the country in the morning, some parts in the west will experience cloudy skies in the afternoon.
Temperatures won't exceed 13C and the peak will be in the afternoon across the whole of Scotland.
Showers will work their way east and become fairly heavy across the Highlands tomorrow night.
Wales
Forecasters say it'll be rainy and windy across Wales tomorrow - but rain will be heavier in the south of the country.
Cardiff will see downpours in the morning and drizzle in the afternoon and into the night.
Any heavy rain across the north of the country will abate by the afternoon though. Temperatures should hit 14C in north Wales by the afternoon but it'll be somewhat colder in the south, with the mercury struggling to exceed 13C.
Northern Ireland
The only yellow weather warning Met Office has in place tomorrow concerns thunderstorms for Northern Ireland. These will be at their strongest at around 7pm, forecasters understand.
It'll be wet before that too, particularly first thing tomorrow morning.
And, as temperatures increase to 18C, the humidity will cause unpleasant conditions as the day progresses.
