Hundreds of schools will fully or partially close over the next few days because of the extreme heat, with temperatures set to hit record highs.
A “heat-dome” settling over western Europe could bring temperatures of nearly 40C by Wednesday, with this latest heatwave expected to surpass the record for June of 35.6C set in Hampshire in 1976.
A red weather warning for extreme heat covering an area stretching from London to Swansea and Somerset to Birmingham was issued by the Met Office from 9am on Wednesday to 9pm on Thursday.
The temperature could come close to the UK’s all-time high of 40.3C which was measured in July 2022.
Met Office spokesman Grahame Madge said: “The Met Office is flagging 39C as a headline maximum temperature on Thursday, most likely for somewhere in London or the South East.
“It is possible we could see temperatures higher than the 39C if the final values are at the upper end of our narrow range.
“It is important to remember that the temperature value is only one element of this extreme heatwave story.
“The other major factor is the high humidity which for many will make the intense heat even harder to endure.”
The temperature in St Athan, South Glamorgan, did not drop below 20.3C overnight on Monday, marking a new record for June in Wales, the Met Office said.
In a post on X on Tuesday afternoon, the forecaster said: “Last night, parts of England and Wales didn’t drop below 20C.
“In fact, Wales has provisionally recorded a new highest minimum temperature for June of 20.3C at St Athan, South Glamorgan.
“Tonight, more areas will remain around 20C, leading to an uncomfortable night’s sleep.”
Extreme heat represents a “dangerous time for older people”, Age UK warned, with statistics showing people aged 75 and over accounted for around nine in 10 heat-related deaths in England last summer.
The weather is also expected to cause major inconvenience to parents as schools shut or close early to protect children from the heat.
Some 100 schools in Somerset will be closed over the next three days, with the vast majority fully closed on Wednesday and Thursday, according to Somerset Council.
Around 100 schools will also be at least partially closed over the next three days in Buckinghamshire, along with 86 schools in Gloucestershire, according to council data.
Children at some schools have been told they can wear PE kit rather than full school uniform, which can involve long trousers and blazers.
Bledlow Ridge School in Buckinghamshire said it was closing as its “classrooms do not have air conditioning, and indoor temperatures are likely to rise significantly above outdoor levels during very hot weather”.
Archway School in Gloucestershire said it could not “safely manage the expected extreme temperatures across the site”, adding that it was “concerned about the risks of travelling to and from school in these conditions”.
Overnight, the temperature did not dip below 20C at nine locations across England, recording what the Met Office class as a tropical night.
The hot weather led to thunderstorms and lightning strikes over England during the early hours of Tuesday.
The Met Office said on Tuesday morning that Somerset had “around 18,540 strikes in the past 24 hours”.
The London Fire Brigade (LFB) received 400 calls overnight, including two house fires believed to be caused by lightning strikes and flooding of homes.
There was also severe disruption across London’s transport network during Tuesday morning.
On the Elizabeth line, heavy rain caused flooding, disrupting services between Heathrow Terminals 2 and 3 and Heathrow Terminal 4.
There were also delays in the afternoon on the Mildmay line, which is running a reduced service because of the hot weather, and on the District line and Metropolitan line because of heat-related temporary speed restrictions.
East Midlands Railway has advised customers to only make essential journeys on Wednesday and Thursday.
Avanti West Coast said it planned to run fewer services than usual between Tuesday and Thursday, and that there was “a risk of further disruption”.
Thameslink said customers “travelling to, from or within extreme heat zones are urged to only travel if absolutely necessary”.
And Chiltern Railways said it had axed more than half its services over the three days “to ensure the safe operation of the railway”.
The extreme temperatures have also forced the Army to cancel ceremonial operations in London and Windsor, to protect the “wellbeing” of its soldiers.
In a post on X on Tuesday morning, the Army in London said: “Due to extreme heat this week, Ceremonial Operations in London & Windsor will be changed or cancelled. The wellbeing of our soldiers, horses and the public will always come first.”
Meanwhile, Natural Resources Wales (NRW) said it had released extra water into the River Dee to help reduce the risk of fish deaths during the high temperatures.
France logged its hottest day on record on Tuesday, the national weather agency Meteo France said, with an average daily temperature of 29.8C across the country.
At least 11 weather stations recorded more than 40C during the day, and the highest temperature of 44.3C was logged in Pissos, in the Landes region, in the south west.
Meteo France said the current heatwave in the country is comparable to that of August 2003, which lasted 16 days.
French Prime Minister Sebastien Lecornu said 40 people have died by drowning in France since last Thursday (June 18), adding they were “mainly young people”.
In the UK, retailers are reporting soaring sales of fans, ice cream makers and sun cream as households try to cope with the extreme heat.
Currys said it had seen an almost 1,500% increase in customers searching for fans on its website compared with last weekend, and a 3,500% increase in searches for air conditioning products over the same period.
Fredi Otto, professor of climate science at Imperial College London, said heatwaves will occur more often and with even higher temperatures “as long as emissions continue”.
She said “our homes, infrastructure, and economy are not built to cope with these conditions”, adding: “The UK has been built for a climate that just doesn’t exist.”
Professor Otto told a media briefing: “Temperatures above 35 degrees used to be extremely rare in the UK.
“They have now occurred in seven out of the last 12 years, and this sustained surge in extreme heat would not have happened without human-caused climate change.”
Dr David Dawson, associate professor in sustainable and resilient cities at the University of Leeds, said heatwaves are going to become “more frequent and longer”, adding that 92% of UK homes could overheat by the 2050s.
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