With temperatures pushing 40 degrees Celsius, the UN warned heatwaves were growing more frequent and intense due to climate change, and called on more countries to put warning systems in place to inform people of the dangers.
At the Safaripark Beekse Bergen zoo in the Netherlands, staff had already put their emergency procedures in place -- including ice cubes for baboons, cold showers for the elephants, and special meat- and fruit-flavoured ice cream for the ring-tailed lemurs.
Humans were having a tougher time, with around a million homes in western France left without power overnight Tuesday after the heatwave moved in from Spain, and another blackout striking Brittany this morning, cutting electricity to 100,000 houses.
The Wimbledon tennis tournament in London saw the hottest day of play ever at 35.7 degrees Celsius, more than a degree hotter than the record set in 1976.
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Defending champion Novak Djokovic remained unfazed: "It wasn't as bad as I thought," he said.
Elsewhere in the city, public fountains became impromptu beaches, with parents sunbathing on benches and children playing in the water in their swimming costumes behind King's Cross station.
Meanwhile in Brussels, it was hard to tell whether European Commission President Jean-Claude Juncker was sweating from the pressure of the Greek crisis or just the ambient temperature.
Another heatwave set to last at least nine days is expected to hit Spain on Friday and then spread to France, Italy, Germany and eastern Europe, the Spanish national weather office said.
Temperatures will be especially high on Monday, reaching 44 degrees Celsius in some Spanish regions, due to the arrival of hot winds blowing from Africa.
The extreme heat carries serious dangers, particularly to the elderly, sick and very young.
The first death directly linked to the heat was reported in the British press after a father drowned while trying to save his young daughter cooling off in a river in the northern Cumbria region.