Sights in the French capital Paris have also been impacted by the hot weather.
The world’s most visited museum, the Louvre, said it would close its doors earlier this week.
The Louvre said its historic building “remains fragile, external and is not sufficiently adapted to climate change”, adding that the “build-up of heat is at its highest at the end of the day, and intensified by the volume of visitors”.
The Eiffel Tower is also closing earlier than usual on Tuesday and Wednesday.
Among those who died in heatwave-related drownings was a six-year-old child who had gone to an unsupervised beach with his parents in Bègles, Gironde on Tuesday evening.
A 17-year-old girl also drowned while swimming in a prohibited area of the Marne river in Champs-sur-Marne, on the outskirts of Paris.
Several drownings have also been reported in Germany, including that of a 26-year-old man who died after going into the Danube River near Regensburg in Bavaria on Tuesday evening.
Emergency services spent hours searching for the Syrian man, who could not swim, using a helicopter and boats. Attempts to resuscitate him after he was found some hours later were unsuccessful.
Temperatures are expected to reach 37C on Wednesday in Germany, and people are being warned not to underestimate the dangers of swimming.
There are also fears of drought in some regions. In Brandenburg, Hesse and North Rhine-Westphalia, authorities are urging people to use water sparingly, German newspaper Die Welt reports.
Barbecue bans have also been introduced in cities including Stuttgart and Freiburg in Baden-Württemberg, local media report.
While Spain has experienced baking heat over the last few days, temperatures are expected to start falling on the Iberian peninsula on Wednesday.
But red heat alerts remain in place for parts of northern Spain, with a maximum temperature of 42C possible in parts of the Basque country, forecaster Aemet said.
In Italy, meanwhile, 16 provincial capitals are now under red heat alerts, with Latina added to the list on Wednesday, while Bari will be added on Thursday, Italian news agency Ansa said.
