Britain is basking in the hottest day of the year so far today thanks to a plume of warm air working its way northwards from Spain.
But the high temperatures brought by the mini heatwave are expected to trigger a series of thunderstorms across the UK overnight into Wednesday, bringing the possibility of extreme rainfall, flash flooding and power cuts.
After the heat of the day, thunderstorms are predicted to bring more than two inches of rain in the space of an hour in some areas, prompting the Met Office to issue a severe weather warning covering almost all of the country.
The forecaster said everywhere north of a diagonal line stretching from Bristol to The Wash could be affected by the extreme weather, with storms potentially causing disruption to travel as well as flooding homes and businesses.
Lightning, hail and wind
In Scotland, frequent lightning, large hail and strong winds could pose additional hazards, with power cuts also a possibility. Drivers have been warned to be alert to the dangers posed by surface water and spray on the roads.
“We are anticipating the most intense activity to be in Wales, northern England and the Midlands, but…there are likely to be impacts for Scotland as well,” said Met Office spokesman Grahame Madge.
“Downpours, where they do occur, could be quite heavy and we believe we could see rain of up to 30mm or so in an hour. If you get a cluster of storms you could see even more than 50mm in an hour in certain areas, which could cause flash flooding in some areas.”
The warm weather means air pollution is likely to worsen across much of the UK on Tuesday and will persist until fresher breezes arrive from the Atlantic on Thursday. There was also bad news for hayfever sufferers, with pollen levels expected to be high for the next few days.
Public Health England (PHE) warned those thinking of enjoying a day in the sun to seek shade between 11am and 3pm, stay cool and drink plenty of water. Others were advised to look out for people who may be struggling in the heat.
“For some people – such as older people, those with underlying health conditions and those with young children – summer heat can bring real health risks,” said Dr Angie Bone, PHE’s head of extreme events. “We’re urging people to keep an eye on those at risk and if you’re able, offer help to stay cool and hydrated."