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The Swelter of Summer: Heat Waves and the Urban Heat Island in New York City History

A history of record-breaking highs but also of sweaty, sticky, corporeal experiences.

The dog days of summer in New York City have inspired classic films, music, and the seasonal rite of open fire hydrants. By the late nineteenth century, heat waves exacerbated the environmental challenges of the city’s urban heat island effect.

The design of New York’s urban core—the orientation and form of buildings and roads—led to the absorption and storage of incoming solar radiation, a meteorological effect known as the urban heat island. The press enthusiastically covered each heat wave that hit the city. When heat waves and the urban heat island collided, journalists announced “[t]orrid waves,” “sweltering periods,” and “red hot terms” in splashy headlines. They wrote lushly of how the “great city roared and steamed and smoked,” and titillated with sensationalist stories of suffering. One journalist took pains to explain that although “Coney Island is only six miles away, there are hundreds of thousands in town, bound to the bricks and the flagging like Prometheus to his rock, who find the city hot enough in all conscience.”

In the urbanized core, far from the Atlantic beaches of Queens and Brooklyn, New Yorkers faced heat waves as an aspect of the summer environment. The breeze-blocking scale and mass of city blocks, the lack of shade, and the urban heat island magnified the feel of seasonal weather, especially during heat waves.

Origin of the Urban Heat Island

Chemist and amateur meteorologist Luke Howard first detailed the urban heat island effect in London in the late-1810s. Fifty years later Dr. Stephen E. Smith, a pioneer of New York’s Metropolitan Board of Health, explained it by detailing how “powerful irradiation from sidewalks, pavements, and walls,” made the city a “fiery furnace in Summer.” In 1899, Smith expanded his observations, declaring it “a well-established fact that the temperature of large and densely populated towns is far higher than the surrounding country” due to “the absence of vegetation… the covering of the earth with stone, bricks, and mortar; the aggregation of population to surface area; [and] the massing together of buildings” of stone and brick, materials prone to heat retention.


Summer Memories

As American cities grew bigger in the 19th century, their residents began to notice one unintended consequences of urbanization, not know as the "heat island" effect. In the 1860s, one NYC official explained that “powerful irradiation from sidewalks, pavements, and walls” made the city a “fiery furnace in Summer."