Southern Europeans braced Saturday for the first heatwave of the northern hemisphere summer, as climate change pushes thermometers on the world's fastest-warming continent increasingly into the red, Azernews reports via France24.

Temperatures are set to rise to 37 degrees Celsius (99 Fahrenheit) in Rome, driving the Eternal City's many tourists and Catholic pilgrims to the Vatican alike towards the Italian capital's 2,500 public fountains for refreshment.

With residents of the southern French port city of Marseille expected to have to cope with temperatures flirting with 40C (104F), authorities in the country's second-largest city ordered public swimming pools to be made free of charge to help residents beat the Mediterranean heat.

Two-thirds of Portugal will be on high alert on Sunday for extreme heat and forest fires, with 42C (108F) expected in the capital Lisbon, while visitors to -- and protesters against -- Amazon tycoon Jeff Bezos's Friday wedding in Venice likewise sweltered under the summer sun.

"I try not to think about it, but I drink a lot of water and never stay still, because that's when you get sunstroke," Sriane Mina, an Italian student, told AFP on Friday in Venice.

Scientists have long warned that humanity's burning of fossil fuels is heating up the world with disastrous consequences for the environment, with Europe's ever-hotter and increasingly common blistering summer heatwaves a direct result of that warming.

The heatwave is forecast to become even more intense on Sunday.

Spain, which has in past years seen a series of deadly summer blazes ravaging the Iberian peninsula, is expecting peak temperatures in excess of 40C (104F) across most of the country.