Millions of people in Britain have woken from the country's warmest-ever night and are bracing for a day when temperatures are forecast to hit 40C, as a heat wave scorching Europe wallops a country more used to mild weather and rain.
The UK's Met Office weather agency said provisional figures showed the temperature remained above 25C overnight in parts of the country for the first time.
A huge chunk of England, from London in the south to Manchester and Leeds in the north, is under the country's first warning of "extreme" heat, meaning there is danger of death even for healthy people.
Hot, dry weather has gripped southern Europe since last week, triggering wildfires in Spain, Portugal and France, before moving north.
The temperature Monday reached 38.1C at Santon Downham in eastern England, just shy of the highest-ever temperature recorded in Britain - 38.7C, a record set in 2019. Tuesday is expected to be hotter.
Average July temperatures in the UK range from a daily high of 21C to a night-time low of 12C, and few homes or small businesses have air conditioning.
Many people coped with the heat wave by staying put. Road traffic was down from its usual levels on Monday. Trains ran at low speed out of concern for buckled rails, or did not run at all. London's Kings Cross Station, one of the country's busiest rail hubs, was empty on Tuesday, with no trains on the busy east coast line connecting the capital to the north and Scotland. London's Luton Airport had to close its runway because of heat damage.
At least five people were reported to have drowned across the UK in rivers, lakes and reservoirs while trying to cool off.
Climate experts warn that global warming has increased the frequency of extreme weather events, with studies showing that the likelihood of temperatures in the UK reaching 40C is now 10 times higher than in the pre-industrial era. Drought and heat waves tied to climate change have also made wildfires harder to fight.
The dangers of extreme heat were on display in southern Europe. Almost 600 heat-related deaths have been reported in Spain and Portugal, where temperatures reached 47C last week.
In the Gironde region of southwestern France, ferocious wildfires continued to spread through tinder-dry pines forests, frustrating firefighting efforts by more than 2000 firefighters and water-bombing planes.
More than 37,000 people have been evacuated from homes and summer vacation spots since the fires broke out July 12 and burned through 190 square kilometres of forests and vegetation, Gironde authorities said.
A smaller third fire broke out late on Monday in the Medoc wine region north of Bordeaux, further taxing firefighting resources. Five camping sites went up in flames in the Atlantic coast beach zone where blazes raged, around the Arcachon maritime basin famous for its oysters and resorts.
But weather forecasts offered some consolation, with heat-wave temperatures expected to ease along the Atlantic seaboard on Tuesday and the possibility of rains rolling in late in the day.
© PAA 2022