Vast swathes of Europe have baked in tropical temperatures that have claimed nine lives in France alone, but summer thunderstorms brought some welcome relief.

A 32-year-old man died in Spain after suffering heatstroke while working on a farm in Caceres in the east, local health authorities said on Thursday. He was Spain's third heatwave victim after a builder died in Murcia in the south on Sunday and a 44-year-old man died on Tuesday in Galicia in the northwest.

Sixteen people have died so far across Europe, where thermometers have hovered over the 30 degrees Celsius mark (86 degrees Fahrenheit) for several days, but authorities in France said that measures implemented following the 2003 heatwave had averted another disaster.

More than 35,000 mainly elderly people died across Europe in 2003, including about 15,000 in France, as a result of dehydration and heat stroke.

In recent days, at least nine people have died from heat-related deaths in France. Germany, the Netherlands and Spain have reported two deaths each.

Parisians got welcome relief from the suffocating heat on Thursday as the city opened its annual artifical beach along the banks of the capital's Seine river.

The four-week-long Paris Plage initiative was extended this year with the creation of another beach on the Left Bank and a second swimming pool where residents and tourists could escape the summer heat.

Britain also sweltered with temperatures rivalling many of Europe's traditional summer hotspots such as Rome or Athens.

The thermometer hit 36.3 C just south of London on Wednesday, the hottest July day since 1911 when records began. The all-time record of 38.5 C, set in August 2003, still stands.

Meteorologists in Britain estimated that temperatures had peaked for the week but many counties, particularly in the south, were still expected to swelter in over 30 C. The average temperature in Britain in July is 22 C.

Denmark also recorded exceptionally high temperatures with beaches and parks packed by residents seeking cool water or shade.

The heatwave has been a boon for many Danish businesses as ice-cream sales have shot up 21 percent, sunglasses by 50 percent and entries to children's swimming pools have increased 25 percent.

But the heat has also brought drought.

Several Polish deputies on Thursday held mass in the parliamentary chapel to pray for rain.

Fires have flared across Europe as baked earth and scorched vegetation have created ideal conditions to fan flames far and wide.

In Portugal, 700 firefighters are battling at least nine separate forest fires across the country in temperatures reaching 41 C.

More than 600 hectares (1,500 acres) of agricultural land was destroyed by blazes in France on Wednesday alone.

In central and northern Croatia, more than 250 hectares of forest and woodland have gone up in smoke over the last two days, local television stations reported.

The head of a French research laboratory said the unusually high temperatures were linked to global warming.

"The rules are changing, there's no doubt about it. This is the start of a process. We can expect heatwaves to be more frequent and more extreme as a result of the general rise in temperatures linked to greenhouse gas emissions," said Herve Le Treut, director of the National Centre for Scientific Research.

Germany said the exceptional heat had increased ozone pollution to potentially harmful levels in parts of the country and only storms could clear the air. "We are at the start of a cycle of ozone pollution," said an official at the federal bureau for the environment.