Spain, France and other western European nations sweltered over the weekend under a blistering June heatwave, with some wildfires still blazing even as the weather began to ease.
The soaring temperatures were in line with scientists' predictions that such phenomena will now strike earlier in the year thanks to global warming.
Emergency services battled several wildfires in northern Spain. The most alarming blaze in the north-western Sierra de Culebra mountain range has destroyed over 25,000 hectares (62,000 acres), the regional government said.
Firefighters said cooler temperatures overnight had helped them make progress in their battle against the flames.
Residents of some 20 villages who were evacuated from their homes were allowed to return home this morning, local officials said.
Temperatures of more than 40 degrees Celsius (104F) have been recorded in parts of Spain throughout the week, but they had dipped by today in most of the country.
The mercury was only expected to hit 29C in Madrid and 25C in the province of Zamora where the Sierra de Culebra mountain range is located.
There have also been fires in Germany, where temperatures reached 36C.
In southern France, a blaze triggered by the firing of an artillery shell in military training burnt around 200 hectares of vegetation, authorities in the Var region said.
"There is no threat to anyone except 2,500 sheep who are being evacuated and taken to safety," the local fire brigade chief said.
The popular French southwestern seaside resort of Biarritz saw its highest all-time temperature yesterday afternoon of 42.9C, state forecaster Meteo France said as authorities urged vigilance from the central western coast down to the Spanish border.
Many parts of the region surpassed 40C, although storms were expected on the Atlantic coast this evening - signs that the stifling temperatures will "gradually regress to concern only the eastern part of the country," the weather service reported.
The baking heat failed to put off heavy metal aficionados attending the Hellfest festival at Clisson on the outskirts of the western city of Nantes, where temperatures soared beyond 40C.
With the River Seine off limits to bathing, scorched Parisians took refuge in the city's fountains.
And at Vincennes Zoo on the outskirts of the capital, shaggy-haired lions licked at frozen blood fed to them by zookeepers, who monitored the enclosure's animals for signs of dehydration.
"This is the earliest heatwave ever recorded in France" since 1947, said Matthieu Sorel, a climatologist at Meteo France, as June records fell in a dozen areas, leading him to call the weather a "marker of climate change".
The UK recorded its hottest day of the year on Friday, with temperatures reaching over 30C in the early afternoon, meteorologists said.
Several towns in northern Italy announced water rationing. The country's dairy cows were putting out 10 percent less milk, the main agricultural association Coldiretti said Saturday.
With temperatures far above the cows' "ideal climate" of 22-24C, animals were drinking up to 140 litres of water a day, double their normal intake, and producing less due to stress, it said.
Experts warned the high temperatures were caused by worrying climate change trends.
"As a result of climate change, heatwaves are starting earlier," said Clare Nullis, a spokeswoman for the World Meteorological Organization in Geneva.
"What we're witnessing today is unfortunately a foretaste of the future" if concentrations of greenhouse gases in the atmosphere continue to rise and push global warming towards 2C from pre-industrial levels, she added.