Spain, France and other western European nations on Saturday sweltered under a blistering June heatwave that has sparked forest fires and concerns such early summer blasts of hot weather will now become the norm.

Saturday's soaring temperatures were the peak of a June heatwave in line with scientists' predictions that such phenomena will now strike earlier in the year thanks to global warming.

The popular French southwestern seaside resort of Biarritz saw its highest all-time temperature Saturday afternoon of 42.9 degrees Celsius (109.2 degrees Fahrenheit), 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 40 degrees Celsius, although storms were expected for the late evening.

Those who found the energy to headbang to the music were grateful for several water fountains on hand which sprayed them periodically.

Queues of hundreds of people and traffic jams formed outside aquatic leisure parks in France, with people seeing water as the only refuge from the devastating heat.

With the River Seine off limits to bathing, scorched Parisians took refuge in the city's fountains.

"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".

Forest fires rage

In a major incident in France, a fire triggered by the firing of an artillery shell in military training in the Var region of southern France was burning some 200 hectares of vegetation, local authorities said.

"There is no threat to anyone except 2,500 sheep who are being evacuated and taken to safety," said local fire brigade chief Olivier Pecot.

The fire came from the Canjeurs military camp, the biggest such training site in Western Europe.

Fire services' work was impeded by the presence of non-exploded munitions in the deserted area but four Canadair planes were deployed to water bomb the fires.

Farmers in the country are having to adapt.

Daniel Toffaloni, a 60-year-old farmer near the southern city of Perpignan, now only works from "daybreak until 11.30a.m." and in the evening, as temperatures in his tomato greenhouses reach a sizzling 55 degrees Celsius.

Forest fires in Spain on Saturday had burned nearly 20,000 hectares of land in the north-west Sierra de la Culebra region.

The flames forced several hundred people from their homes, and 14 villages were evacuated.

Some residents were able to return on Saturday morning, but regional authorities warned the fire "remains active."

Firefighters were still battling blazes in several other regions, including woodlands in Catalonia. 

Temperatures above 40 degrees Celsius were forecast in parts of the country on Saturday – with highs of 43 degrees Celsius expected in the north-eastern city of Zaragoza.

There have also been fires in Germany, where temperatures were forecast to go as high as 40 degrees Celsius on Saturday, although only reached 36 degrees Celsius. A blaze in the Brandenburg region around Berlin had spread over about 60 hectares by Friday evening. 

Foretaste of future 

The UK recorded its hottest day of the year on Friday, with temperatures reaching over 30 degrees Celsius in the early afternoon, meteorologists said.

Several towns in northern Italy have announced water rationing and the Lombardy region may declare a state of emergency as a record drought threatens harvests.

Italy'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 22-24 degrees Celsius, animals were drinking up to 140 litres of water per 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 two degrees Celsius from pre-industrial levels, she added.