France braced for another heatwave, with Paris on Wednesday allowing swimming in one of its canals so residents could cope with the temperature.
It will be the second spell of unusually hot weather this year, after a scorching week in May smashed records in half the country.
"A heatwave episode will gradually set in across the country this week," said Christelle Robert, of national weather service Meteo-France.
Temperatures hit 37C in some areas on Wednesday, and are expected to peak at 40C in some regions on Sunday as the country celebrates summer solstice with its annual nationwide music festival, "La Fete de la Musique".
The national weather system issued a heat-wave alert late Wednesday for the following day, saying temperatures would be unusually high in the Paris region and most of the country's east.
The high temperatures come as students across France are taking their high school final exams. Shorts, T-shirts and baggy clothing were the norm as students filed into the Saint-Exupery high school in Lyon.
In Paris, swimming was allowed from Wednesday evening under lifeguard supervision in one part of the Canal Saint-Martin, in the east of the city.
Youth plunged into the canal during the scorching week last month.
"Spending an enormous amount of energy, municipal police and national police to stop young people from swimming when it was 40 degrees... struck us as slightly absurd," Paris mayor Emmanuel Gregoire said on Tuesday evening, however reminding youth that jumping from bridges was dangerous and remained forbidden.
Alexandra Cordebard, the mayor of the capital's 10th district, said allowing swimming in the canal earlier than scheduled in July was "a new way of fighting climate change and adapting the city".
In summer, swimmers will also be able to cool off at designated points along the Seine River, after it reopened to swimmers last summer for the first time in a century.
Paris had poured more than a billion euros ($1.15 billion) into getting the river clean enough to use during the 2024 Olympics.
Studies and scientific bodies agree that heatwaves in Europe are becoming more frequent as a consequence of climate change.
Meteo France says that of the 51 heatwaves recorded nationwide since 1947, 34 have occurred since 2000 and 26 since 2011.
Global average temperatures are likely to continue at or near record levels this year and for the next four years afterwards, the United Nations has warned.
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