At least 40 people have drowned in France over the last five days as the country endured a scorching heat wave, Sébastien Lecornu, the country’s prime minister, said at an emergency cabinet meeting on Tuesday.

Most of the drowning victims were young, many of them teenagers, and swimming in unsupervised areas. Mr. Lecornu called the drownings a “tragic scourge.”

Marina Ferrari, a minister whose responsibilities include young people, said in an interview on French radio on Tuesday that the drownings were mostly in bodies of water such as lakes or canals.

“During heat waves like this,” she said, “it’s no small matter to go swimming in areas that aren’t supervised.”

France is in the middle of an intense heat wave over much of Europe that began in the middle of last week. Forecasters have said that Paris could hit 40 degrees Celsius this week (104 degrees Fahrenheit), not far from its record. Parts of central France could see highs of 43 degrees Celsius (around 109 degrees Fahrenheit).

More than half of the country is under a red alert for heat wave conditions, the most severe. France’s weather agency, Météo-France, said that it expected “exceptionally high temperatures, both day and night.” The temperatures have the potential to have a “strong health impact.”

“All the records, locally or nationally, are being broken every day or night when it comes to temperatures,” Mr. Lecornu said.

The current heat wave in Europe is the result of a “heat dome,” a strong area of high pressure that allows heat to build over a region.

According to Météo-France these stubborn, high-pressure systems can block or divert passing weather fronts, leading to conditions with few clouds and little rainfall

For France, this is the second heat wave in about a month, after record-breaking temperatures in May.

The high temperatures have also caused other fatalities over the last few days. BFMTV, a French news station, reported the deaths of two children — ages 2 and 4 — who were left inside a car on Monday.

Aurelien Breeden contributed reporting from Paris.