Recently released from coronavirus lockdown, Europeans thronged shady parks on Wednesday as temperatures soared on the second day of an early summer heat wave that experts fear will lead to new infections as people flout social distancing rules.

The European Meteorological Service issued a warning of extreme temperatures from the south to the usually cooler north of the continent -- with "dangerous" heat forecast for parts of Spain where the mercury could climb as high as 38 degrees Celsius (100 degrees Fahrenheit).

People enjoy the sun in a Paris park, but experts fear a surge in coronavirus infections
People enjoy the sun in a Paris park, but experts fear a surge in coronavirus infections AFP / Christophe ARCHAMBAULT

Seven other countries risked less extreme but "potentially dangerous" warm weather: Belgium, Estonia, Finland, Latvia, the Netherlands, Portugal and Sweden, it said.

Brought to Europe by a high pressure system, this was a "short episode" of heat that will last only until the weekend, according to meteorologist Cristina Simoes of Portugal's Lusa weather agency.

As the mercury started climbing Tuesday, beaches, parks and river banks saw an influx of hot and bothered Europeans, with images of large groups gathered often without masks or the required one-to-two-metre (3.3-6.6-foot) infection-safe distance between them.

"It's a bit like the holidays": Paris is experiencing its first heat peak of the summer
"It's a bit like the holidays": Paris is experiencing its first heat peak of the summer AFPTV / Mathieu CHAMPEAU

In Britain, where temperatures are expected to approach -- but not break -- the 35.6C record set for June in 1976 -- health officials have expressed concern about the continued defiance of social distancing requirements.

Social care workers are also worried about elderly people shielding from the virus at home in the stifling heat.

"It can be harder to spot someone who may be getting into difficulties and in need of extra help," said Caroline Abrahams, director of the Age UK charity.

Europeans have thronged parks and rivers, as here on the banks of the River Seine in Paris, as the rising mercury announces the start of summer
Europeans have thronged parks and rivers, as here on the banks of the River Seine in Paris, as the rising mercury announces the start of summer AFP / STEPHANE DE SAKUTIN

In France, the weather agency expected temperatures to exceed 30C in most of the country, going as high as 36C in the southwest.

Temperatures in the thirties in France are usual for the height of summer, around August, and not the beginning of the season, said climate NGO CARE.

"Over the past few years, we have noticed heat waves arriving ever earlier, everywhere in the world," it said in a statement, blaming global warming.

"A few days ago, a temperature of 38C was recorded north of the Arctic Circle! Such high heat phenomena could be twice as frequent by 2050, so we must expect summers to be ever longer and hotter, and therefore more deadly."

The World Meteorological Organization has said it was verifying the worrying temperature record for Siberia.

The World Health Organization warned people to avoid exposure to the sun or temperatures higher than 25C "as there is no evidence that this prevents or cures COVID-19, and it increases your risk of sunburn and heat-related illness.

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