France struggles with extreme heat and power grid challenges as temperature records also smashed in parts of UK and Spain.

French authorities say about ⁠20 ⁠people have drowned over the weekend while swimming in unsupervised areas to seek relief from a heatwave gripping France and other parts of Europe.

“To go swimming in unauthorised areas during a ‌heatwave is not something to take lightly,” Sports Minister Marina ⁠Ferrari told France ⁠Inter radio as forecasters said temperatures in much of the country would reach about 40 degrees Celsius (104 degrees Fahrenheit) ⁠on Tuesday.

Separately, local authorities said the heatwave was the most likely reason for the deaths of two children aged two and four who were found unconscious in a car outside their home in Carpentras in southeastern France.

Three more people aged 80 to 95 died in the Bordeaux region from heat-related health issues, local official Sophie Brocas told France TV.

The heatwave smashed temperature records in multiple cities, including Bordeaux and Poitiers, and strained power grids and public services. The national weather service placed 54 areas of France, a country without widespread air conditioning, under a red heatwave alert while schools closed early or adjusted timetables to protect students.

Elsewhere in Europe, Britain’s Met Office warned on Monday that a four-day heatwave could push temperatures above 39C (102F) in parts of the country, easily breaking the June record of 35.6C (96F) set in 1957 and 1976.

Just weeks earlier, the United Kingdom had recorded its highest May temperature on record.

“Thirty-six degrees is going to be disgusting,” data scientist Lewis Jennings told the Reuters news agency in London. Forecasters said temperatures would run 5-10C (9-18F) above normal with northern areas seeing even larger anomalies.

Spain also saw extreme heat. San Sebastian in the traditionally cooler north was set to reach 40C 104F), more than double the city’s historic average for June 22, according to the Reuters Climate Monitor.

The monitor showed Europe as the continent furthest from its historic norm on Monday.

The extreme heat was driven by an “Omega block” weather pattern, named for its resemblance to the Greek letter shape. The system has trapped a bulge of hot air over the continent while cooler air sits on either side.

“It’s drawing warm air up from North Africa, from the Sahara, and that’s why we have this really intense ⁠heat. It’s very slow moving, and it means there’s kind of no wind, no breeze for respite,” Clair Barnes, a research associate in extreme weather and climate at Imperial College in London, told Reuters.

Heatwaves and storms ⁠are being intensified by climate change, pushing temperatures higher and causing more rainfall, she said.