Attractions in the French capital Paris were also affected by the hot weather.
The Louvre, the world’s most visited museum, said it would close earlier this week.
“The historic building remains vulnerable and, externally, has not sufficiently adapted to climate change,” the Louvre said. “Heat build-up is highest at the end of the day and becomes more severe as the number of visitors increases.”
On Tuesdays and Wednesdays, the Eiffel Tower also closes earlier than usual.
Among those who died from heatwave-related drownings was a six-year-old child who went to an unsupervised beach with his parents in Begl, Gironde, on Tuesday evening.
A 17-year-old girl also drowned while swimming in a restricted area of the Marne River in Champs-sur-Marne, outside Paris.
Several drownings were also reported in Germany, including a 26-year-old man who died after falling into the Danube River near Regensburg, Bavaria, on Tuesday evening.
Emergency services spent hours using helicopters and boats to search for the Syrian man, who cannot swim. Attempts to resuscitate him after he was found several hours later were unsuccessful.
In Germany, temperatures are expected to reach 37C on Wednesday and people are being warned not to underestimate the dangers of swimming.
There are also concerns about drought in some areas. German newspaper Die Welt reported that authorities in Brandenburg, Hesse and North Rhine-Westphalia are urging people to use water sparingly.
Barbecue bans have also been introduced in cities including Stuttgart and Freiburg in Baden-Württemberg, according to local media reports.
Spain has been experiencing heat waves for the past few days, but temperatures are expected to start dropping on the Iberian Peninsula from Wednesday.
However, red heat warnings remain in place for northern Spain and temperatures could reach up to 42C in some parts of the Basque Country, forecaster Aemet said.
Meanwhile, in Italy, red heatwave warnings are currently in effect for 16 regional capitals, with Latina added to the list on Wednesday and Bari scheduled for Thursday, Italian news agency Ansa reported.
