LONDON — Never in recorded history has Paris been hotter than it was on Thursday, when the temperature neared 110 degrees. The same was true of Belgium, Germany and the Netherlands, as a dangerous heat wave scorched Western Europe.

Parisians could be seen plunging fully clothed into the fountains of the Trocadéro, Viennese cooled themselves in municipal misters, and Amsterdamers dangled their feet in a repurposed kiddie pool at a cafe. But here is what is far less likely to be seen: air-conditioners.

That’s because the technology that transformed American homes and offices over the last century still gets a chilly reception in much of Europe.