It was the middle of June, and Emmanuel Grégoire, the newly elected mayor of Paris, was installed on the banks of Canal Saint-Martin, surrounded by shirtless Parisians, set to perform his John the Baptist drag. Lyas, a curly-haired twentysomething influencer, outstretched his arms, ready, in his tattered “fashion pas facho” T-shirt—“fashion not fascist,” in English—to receive a playful palm to the chest from the Mayor, which sent the influencer straight into the water. The other bathers followed suit.

Likely to his annoyance, Grégoire, who is forty-eight, and a member of the Socialist Party, is not the first Parisian mayor to stage an opening of the waters in this city, which is warming at disaster-film-montage pace, and which is not prepared for the current heat wave. That distinction may belong to Anne Hidalgo, Grégoire’s predecessor, under whom he served as deputy mayor, and with whom he had a political falling out that weighed him down for some years with the unfortunate title “ex-dauphin,” given to him by the press.

On the eve of the 2024 Summer Olympics, hosted by Paris, a wetsuited Hidalgo had plunged herself into the Seine. More than a billion dollars had been allocated for the cleaning of the river in time for the Games; the following summer brought the establishment of three swimming zones in the Seine, lifeguards included. Grégoire was, in mid-June, inaugurating similar zones in the Canal Saint-Martin, presenting them as urbane oases in a direct response to a miserable heat wave that had hit the city, a couple of weeks earlier, in May, when a North African heat dome swallowed the entire country, and temperatures reached thirty-six degrees Celsius, or ninety-seven degrees Fahrenheit, at their peak.

May was nothing; Grégoire and the bathers and every other person were in for something else at the end of June, when a heat wave blanketed France, Germany, the U.K., Belgium, the Czech Republic, and the Netherlands. A pedestrian, willfully ignorant of the exact temperature on Wednesday afternoon, happened to glance at a flashing L.E.D. sign outside a French pharmacy. It read forty-five degrees Celsius, or a hundred and thirteen degrees Fahrenheit. Her jaw dropped, cartoon-style. The heat stole into her mouth, stuffing her like cotton. Breathing eluded her; she felt like vomiting the heat out. It had been only ninety degrees or so that morning.

“La Canicule,” the term that the French have used to describe an elongated spell of oppressive, often dangerous temperatures, doesn’t really translate to “heat wave”—the phrase for that would be “vague de chaleur.” The spirit of La Canicule is more like dog days. Typically, the dog days arrive in late July or August, when the country winds down for its prolonged weeks of vacation. And those days tend to hover some twenty degrees Fahrenheit lower than what it is experiencing now. La Canicule is an old term, a cheeky one, just newly representative of the climate crisis.

“Good Morning America” milked a decline-of-the-Occident comparison, highlighting the fact that parts of France, for a brief period, were hotter than the Sahara Desert. In Paris, signage exhorts Métro riders to hydrate regularly, stay attentive to those who are most vulnerable, et cetera. At one underground station, the Stalingrad, tent settlements of nearly a thousand people sleep rough. Hundreds of schools have closed. The shops, if they have decided to remain open, have draped their windows with reflective blankets, to deflect light particles. Many restaurants have forgone opening during the day altogether, a handwritten sign indicating that they’ll start seating customers after 7 P.M., when the temperature approaches something closer to tolerable. The Louvre has closed early, as has the Eiffel Tower. Moist towels soothe necks, mist bottles spray short relief, hand fans flap in overdrive; motorized fans are held up to strangers at cafés, who have resorted to pouring water directly on their chests for cooling. What is a more elemental influence over human behavior than weather? Commiseration is the tone here; in other public spaces, like the supermarket, fights have ensued. At one café, a van pulled up as the diners spoke to one another about the heat. The driver opened the back door and pulled out a gurney. A refrigerated compartment was visible in the back of the vehicle; he was here to take a body to the morgue. A café customer chimed in, “Welcome to Paris.”