Summer does not officially begin until June 21st, but the temperature reached ninety degrees in New York City last Wednesday. Here, the heat possesses a special, withering oppressiveness: from the sidewalks below, the concrete canyons of the city come to resemble the contours of a giant tandoor oven. As Arthur Miller wrote in the magazine, in a piece about the summer heat, “The city in summer floated in a daze that moved otherwise sensible people to repeat endlessly the brainless greeting ‘Hot enough for ya? Ha-ha!’ It was like the final joke before the meltdown of the world in a pool of sweat.”

New York City has a randomly outsized role in what is perhaps the twentieth century’s most taken-for-granted innovation. In 1889, Alfred R. Wolff designed a ventilation system for Carnegie Hall, which employed blocks of ice and steam-powered blowers to cool its patrons. Essentially, the air from the blowers flowed over the ice, cooling the space. Ten years later, he designed a system for the dissecting room of Cornell Medical College that more directly prefigures the invention that would come to be known as the beginning of modern air conditioning; a refrigeration unit circulated a brine solution through pipes, over which air was blown to cool the fifth-floor lab. (Though meant to keep cadavers from rotting, inevitably it was used by students to escape the heat.)

Willis Carrier is widely credited as the inventor of modern air conditioning for engineering his “apparatus for treating air,” in 1902. Crudely speaking, it worked by blowing air over a set of coils filled with a coolant. The intent wasn’t to chill the suffocating summer air into a pleasant breeze for sweltering humans. Rather, the device was built to precisely control the humidity of the air inside a Brooklyn printing plant owned by the Sackett-Wilhelms Lithographing and Publishing Company; the vacillating humidity levels caused paper to shrink and swell, complicating the printing process. (The building still stands, in the neighborhood of Bushwick.) Humidity, not temperature, was front of mind for most of the first engineers of what came to be called air conditioning, according to Gail Cooper, a professor of history at Lehigh University. In her study, “Air-Conditioning America,” she writes, “Once engineers found the means to regulate humidity, they claimed that alongside the other technical marvels of the modern era, they had finally achieved mastery over the weather as well.”

The first space that was cooled with modern air conditioning specifically for the comfort of sweaty people was the trading floor of the new building for the New York Stock Exchange, which opened in 1903. Designed by Wolff, it relied on three ammonia-absorption machines, each with a cooling capability equivalent to a hundred and fifty tons of ice. Like all early air-conditioning systems, it was meant for industrial use and deeply integrated into the architecture of the building. Cooper notes that Wolff, who became the leading air-conditioning engineer in New York City, installed just three residential systems in total—for the Vanderbilt, Carnegie, and Astor residences.

The first true home air conditioner was not developed until 1929. The system required both a four-hundred-pound sulfur-dioxide-condensing unit and a two-hundred-pound cabinet to function, and it cost thousands of dollars to install. Air conditioning for the masses was not possible until Henry Galson invented the far more compact and inexpensive self-contained unit, in the early nineteen-thirties, decades after the first systems by Carrier and Wolff. The thrill has not faded from this description of the machine, published in a 1935 issue of Popular Mechanics: “Compact and so low in height that it fits below the window sill of the average home or office, a self-contained air-conditioning unit is ready for the market.”

Within five years of the release of Galson’s portable air conditioner, Philco-York started marketing what became the “first successful model of a window air conditioner,” writes Vaclav Smil in “Creating the Twentieth Century.” Its Cool-Wave line of air conditioners included models that cost as little as a hundred and fifty dollars—“the mere price of a good radio!” enthuses one 1939 ad—and could be plugged into a standard power outlet. They were also relatively portable: while a window-mounted unit produced in 1937 by Pacific weighed three hundred and fifteen pounds, a 1939 ad for a C.W.-40 lists a shipping weight of a hundred and ninety-five pounds.

Air-conditioning adoption boomed after the Second World War as prices fell precipitously. By 1962, Donald Malcolm lamented, in a June Talk of the Town piece, the “countless thousands of these machines pumping heat into the streets” and believed that “their use in summer ought to be strictly forbidden.”

The windows of apartment buildings still sprout air-conditioning units like a citywide fungal infection every summer, since centralized air conditioning in private homes remains a relative luxury in New York City. Con Edison estimated, in 2012, that there were over six million window units in use in its service area, which includes virtually all of New York City and most of Westchester County. It expects peak demand for electricity this summer to reach thirteen thousand and two hundred megawatts; the current record is thirteen thousand one hundred and eighty-nine megawatts, set on July 22, 2011. With the National Weather Service’s Climate Prediction Center forecasting temperatures to be slightly above average this summer, it’s clear that things are just warming up.

Photograph: Carrier Corporation/AP.