Forty people have drowned in heatwave-related deaths in France since last Thursday, Prime Minister Sébastien Lecornu has said, as temperatures hit record levels in several major cities and the heatwave reaches a peak in several European countries.

"It's not something to be taken lightly, going swimming in unsupervised areas during a heatwave," sports and youth minister Marina Ferrari told French radio.

France, along with Spain and Italy, have been hardest hit by the heatwave so far.

France saw its hottest June day on record on Monday and its hottest ever night on Monday night, with a minimum average of 21.6C according to Météo France, and with well over half the country on red alert.

Meanwhile, in Spain temperatures are set to peak above 40C in some areas, with red alerts in Andalusia in the south, and Cantabria and the Basque Country in the north, on the third day of a national heatwave.

Spain is more exposed to the effects of climate change than almost any other European country. State weather service Aemet says June heatwaves are becoming increasingly common, with 10 recorded in mainland Spain between 2000 and 2025, and just two in the previous 25 years.

And in Italy, a red heatwave alert has been declared in 15 cities, including Rome, Milan, Florence, Turin and Venice. The alert signals conditions that can pose health risks even to healthy adults, not just the elderly or chronically ill.

France's sports minister said too many people were trying to cool off in rivers and canals without necessarily taking the risks into account.

Among the fatalities was a 13-year-old girl who had gone for a dip with her family in the River Seine at Fontaine-La Port on Sunday evening, although she did not know how to swim.

Meanwhile, a young professional footballer was in critical condition in hospital after being pulled out of the River Rhône in a park near Lyon. Emergency services were called to the area to rescue four young men who had got into difficulty in an area of the river where swimming is banned.

Two other deaths on Monday were also blamed on the extreme heat in France, after children aged two and four were found in their family car in a car park in the southern city of Carpentras.

Several people have also drowned in Germany as temperatures are expected to climb as high as 40C in the west and south-west by the end of the week. The German Lifesaving Association (DLRG) said there were six fatal swimming incidents between Friday and Sunday with men in particular were overestimating their abilities in the water.

Spain's Aemet weather service says temperatures could top 44C in rural areas near the southern city of Córdoba on Tuesday, while in the Ebro valley in the north-east they could exceed 42C. In 101 of Aemet's 828 weather stations, temperatures hit or exceeded 40C on Monday, with 45C recorded in Andújar.

"There is evidence that heatwaves were now taking place more frequently at the start of summer than in previous decades," Aemet's Rubén del Campo told Spanish media.

In Italy the government has revived emergency labour protections aimed at protecting workers most exposed to the sun, including farm and construction workers, from having to work through the hottest hours.

Companies that halt or reduce operations because of dangerous heat waves can now access state-backed furlough support.

The heatwave also meant a nuclear power plant in southwest France had to be shut down on Monday night because water temperatures in the River Garonne were set to reach 28C on Tuesday. Under French laws, water used to cool the reactors at the Golfech plant must not exceed that temperature.