Portugal, whose bucolic landscape reveals rolling hills speckled with olive trees and centuries-old stone villages, became a landscape of fear this summer. When a heat wave began to steamroll the country in early July, residents were forced indoors to take what refuge they could behind drawn shutters while outside the heat continued to bake forests and crops already parched from a prolonged drought.

Aided by swift winds and dry conditions, the intense heat sparked dozens of wildfires across the country and in neighboring Spain. Portuguese farmers fled the flames carrying sheep on their backs. Near the Quinta do Lago golf resort in the south, drivers had to turn back as flames and smoke eddied across highways. Even in areas not directly touched by the flames, such as the coastal city of Aveiro, residents struggled to breathe as smoke from fires raging a few miles to the east enveloped some neighborhoods. Thousands were evacuated from their homes across the country.

As blazes burned across Portugal, the searing heat smashed records. In Pinhão, a picturesque village perched on the banks of the Douro River in North Central Portugal, temperatures hit 47.2 degrees Celsius, according to reports from the Portuguese Institute of the Sea and Atmosphere.

Suspected heat-related deaths began to mount. Spanish health authorities have reported a total of 3,952 excess deaths related to the summer’s heat waves. Similar figures haven’t been released for Portugal yet, but at the height of its first heat wave, between July 7 and July 18, the Portuguese health ministry reported that there were 1,063 more deaths than would have been expected for this period.

Even as crews managed to contain some of Portugal’s worst wildfires, the heat continued to cook the northeast of the country, as well as much of Spain and parts of France, Greece, and Turkey. The extreme weather then expanded northward to the UK, where the Meteorological Office issued its first-ever red warning for exceptional heat in the typically cool, wet country, urging residents to brace for temperatures as high as 40 degrees Celsius—a record-breaking first for England that arrived a few days later.

“Temperatures hopping up into the mid-40s does not happen too often, even in Spain or in Portugal,” says Paul Hutcheon of the UK Met Office. Luton airport, which serves London, had to temporarily suspend flights after part of its runway buckled in the heat, while fires broke out across the country.

“The infrastructure is just not built for temperatures of up to 40 degrees Celsius,” says Friederike Otto, a climatologist at Imperial College London’s Grantham Institute for Climate Change and the Environment. “Buildings, schools, and hospitals are neither air conditioned or insulated. Houses don’t have shutters or anything to keep out the heat. People are not aware of the dangers of the heat, and they don’t know how to deal with it.”

While heat waves have occurred in Europe on occasion, they’re becoming far more frequent and intense, and are sticking around for longer. And climate change is largely to blame. When a heat wave swept across Europe in 2019, Otto—who coleads World Weather Attribution, a research collaborative that analyzes climate change’s contribution to extreme weather events—immediately conducted an assessment with her team to see if they could detect global warming’s fingerprints. They did: Climate change made the high temperatures five times more likely, they found.