Thursday, French officials recommended prudence as a record pre-summer heatwave stretched across France from Spain, where authorities were battling forest fires for the sixth day in a row.

Meteo France reported that it was the earliest heat wave in history. It exacerbated a drought induced by a dry winter and spring and increased the risk of wildfires.

Spain, which has already had its warmest May since the turn of the century, was sweltering in temperatures as high as 43 degrees Celsius (109 degrees Fahrenheit), with no relief expected until Sunday, according to the Aemet meteorological service.

At least three forest fires broke out in Catalonia, including one in Baldomar, approximately 140 kilometers (87 miles) northeast of Barcelona, which has burned nearly 1,000 hectares (2,470 acres) and might expand to 20,000 hectares before being contained, according to the regional government.

No evacuation orders have yet been issued, but residents are asked to remain in their homes.

Neighbouring Most experts attribute the early season heat across Europe to global warming driven by greenhouse gas emissions, as Portugal saw its warmest May since 1931.

Climate warming, according to scientists, has made heat waves more likely. As global temperatures continue to rise, it is anticipated that heat waves will become more frequent, powerful, and long-lasting and that their effects will grow more widespread.

'Worst I've ever seen'

Tuesday, the heatwave crossed the Pyrenees into southern France and was expected to affect the majority of the country by Saturday, when temperatures in Paris could reach 39 degrees Celsius.

Friday, the education ministry encouraged parents of younger pupils to keep them at home if possible, as the majority of France was under a heatwave alert, including 12 departments in the southwest at the highest category.

"Be alert! Prime Minister Elisabeth Borne tweeted, "Remain hydrated, stay in cool areas, and stay in touch with your loved ones."

Officials in Paris and other cities have also issued warnings about ozone pollution, which happens when carbon emissions are transformed into smog by bright sunshine.

On Friday, Didier Lallement, the chief of police in Paris, reduced speed restrictions in the region by 10 kilometers per hour (6.2 miles per hour).

"I'm 86 years old and was born here, but I believe this is the worst heatwave I've ever experienced," Jacqueline Bonnaud told AFP in a shady park in the southern city of Toulouse.

According to grid operator RTE, France was forced to import power from neighboring countries due to the rising use of air conditioners and fans, as many of the country's nuclear reactors were offline to analyze potential corrosion hazards or for maintenance.

'Infrastructure suffers'

Because water used for cooling reactors is too hot to be returned to waterways without threatening plants and animals, several nuclear plants must cut output due to falling river levels.

Recently, Spain, Italy, and other nations have restricted the use of air conditioners to conserve energy. French Energy Minister Agnes Pannier-Runacher stated on France 2 television that she is considering doing the same.

Meteo France forecaster Tristan Amm told AFP that Saturday would be the hottest day, with temperatures ranging from 35 to 39 degrees in most of the country.

Schools have stocked up on water and relocated end-of-year tests to rooms facing north, while some departments in the south have canceled Friday afternoon courses.

Cities, including Bordeaux, have installed misting units on the hottest squares and streets.

The French rail operator SNCF has warned of probable delays as trains are forced to decelerate due to heat-damaged tracks and electrical components.

Wednesday's track-level temperatures in Bordeaux reached 52 degrees Celsius (126 degrees Fahrenheit), according to Thierry Rose, regional director of SNCF. "Our infrastructure suffers" from the heat, he said, noting that track-level temperatures reached 52 degrees Celsius (126 degrees Fahrenheit) on Wednesday.