When Alison Fullerton and her husband Jay lived in Europe for three years, it was gripped by a series of summer heatwaves. The couple who have since moved back to Tennessee bought a cute, portable air conditioner they called R2D2 because their house in Stuttgart, Germany, had no air conditioning.

There was just an attitude that we all have to do our part to take care of mother earth, Alison Fullerton said. If we complained, theyd say, Its not bad. Its only a couple weeks of the year. Americans want everything to be easy.

Much of Europe, especially northern Europe, is notorious for its lack of air conditioning notorious, at least, among the occasional Americans who book a trip during a summer heatwave and come to regret it.

These days, 90% of households have air conditioning in the U.S., where the high temperatures in southern areas can average over 90 degrees Fahrenheit in the summer. But with A/C, homes, office buildings, subways and shopping malls often remain icy. Meanwhile, across much of northern Europe, residents are accustomed to sweating indoors.

The U.S. had 374 million household air conditioners in 2016, according to the International Energy Agency (IEA), an intergovernmental research group. Thats 23% of the worlds installed air conditioners. Europe had 97 million 6% of the worlds total.

Green building executive Rick Fedrizzi saw and felt the difference firsthand when attending a meeting recently in a German office building where the room was about 80 degrees Fahrenheit. The Germans were not complaining, he said. The Americans were doing anything to cool off, fanning themselves, drinking ice water, hoping the meeting would be over quicker.

For many Europeans, A/C is just not part of the culture in the same way as it is in the U.S. Harry Koninis, a Greek marketing executive who recently moved to Bonn, Germany, has no air conditioning in his apartment or office and no plans to get any. Its not good for the environment. You also are spending a lot [of money] on energy, he said, adding, Its almost unnatural to have such a cold temperature.

But it appears that not everyone on the continent remains as resolute. As climate change makes scorching summers both more likely and more intense, theres evidence that even Europes resolve against air conditioning may be breaking. Sales of air conditioners in France soared during a few hot days this June in the case of one large French retail chain, by 300% more than the same time last year according to retailers speaking to the local press.

The methods that Europeans have traditionally used to keep their buildings cool may not be enough against extreme heat. Concrete construction and stone buildings that are hundreds of years old are common throughout much of Europe. They stay cool if theres only one hot day, but now that Europe is experiencing more frequent and prolonged high temperatures, the buildings retain the heat and dont have the chance to cool down, explained John Dulac, an energy analyst at the IEA.

If you have one hot summer, you may bear it, he said. When it starts happening every year, youre more likely to go out and buy an A/C.