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

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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.1 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.”2

Crowds at Coney Island during a summer heatwave at the turn of the century.
Bain News Service, Publisher. Crowds at Coney Island. July 5. Photograph. https://www.loc.gov/item/2014688307/.

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.3 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.”4 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.5

Tenement dwellers sleeping on roofs and windowsills.
New York City – The recent “heated term” and its effect upon the population of the tenement districts A night scene on the East Side / / from sketch by a staff artist. New York, 1882. Photograph. https://www.loc.gov/item/96506782/.

263 Heatwave Events

New York City’s daily summer temperatures average around 80°F/26°C in July and August. From June through September, heat waves create higher highs that ruthlessly test residents’ thermal comfort in the urban heat island.6 The U.S. National Weather Service has identified 263 heatwave events via Manhattan’s Central Park weather station records between 1876 and 2011. Such heat events typically lasted three to five days, although the city famously suffered through its first week-plus heat wave in 1896.7 Typically, “dead, suffocating, peppery, motionless, blistering” weather accounted for a dozen days and half as many nights each year.8

What is a Heatwave?

“The severity of historic heat waves is difficult to reconstruct. One challenge is that no standard scientific definition of a heat wave exists.”

The severity of historic heat waves is difficult to reconstruct. One challenge is that no standard scientific definition of a heat wave exists. Alvin T. Burrows first characterized a heat wave as a period of three or more days of temperatures greater than 90°F/32°C in 1901.9 Today the National Weather Service offers no specific temperatures, since what constitutes an “abnormal” level of heat and/or humidity is locally specific.10

Another challenge is the absence of long-term, quality-controlled humidity data— temperature records alone do not suffice. New York City’s average relative humidity of 63% compounds the feel of summer heat (an effect known since 1979 as the heat index).11 For example, air temperature of 90°F/32°C with 45% humidity feels like 93°F/33°C—the same air temperature with 70% humidity, however, feels like 105°F/40°C. A final challenge in reconstructing historic heat waves is that weather records often lack key meteorological variables such as the strength and direction of the breeze, turbulence, cloud cover, and radiant heat, all of which impact the feel of summer weather.12

Surf bathing circa 1900, New York
Detroit Publishing Co., Publisher. Surf Bathing. United States New York New York State, None. [Between 1900 and 1905] Photograph. https://www.loc.gov/item/2016800454/.

Heatwaves: Science v. the Human Sensory Experience

“Since the late nineteenth century residents have known official temperature records were different than bodily experiences of high temperatures.”

Not only are past heat waves difficult to reconstruct, official weather data does not necessarily offer a full accounting of New Yorkers’ experiences of heat waves in the urban heat island. Since the late nineteenth century residents have known official records were different than bodily experiences of high temperatures. Following the ten day August 1896 heat wave, when daytime temperatures averaged above 90°F/32°C, nighttime temperatures held above 70°F/21°C, and interior temperatures were estimated to reach 120°F/48°C, Scientific American pointed out that record books would not necessarily reflect the way the urban heat island magnified this heat. Official weather recordings were taken atop a Manhattan skyscraper, 298 feet above sea level, to remove “instruments… from the local variations which are caused by radiation and reflection from the pavements and walls of the city below.”13 But at street level, New Yorkers experienced localized high temperatures that tied bodily discomfort to urban form and the heat it stored and re-radiated.

"The Thermometer and the Weather Bureau," William Inglis, 1911, breezes from the harbor are exaggerated as freezing wind currents and icicles; station employees dress in the gear of the famous Antarctic explorers of the early 1900s. The data scientists dress in windproof canvas smocks, gloves, and headgear, including goggles. Icicles grow from their beards.
, the men in front of the Weather Station sweat through wilted collars and remove their hats and jackets. Hair styles fall flat and stick to sweaty foreheads. To illustrate heated air, the artist plays up bodily response and emotions. The crowd is uniformly wide-eyed, dazed by the temperature
The feel of the street versus the recordings of the weather station. William Inglis, “The Thermometer and the Weather Bureau,” Harper’s (Aug. 19, 1911), 13.

In an August 1911 heat wave Harper’s emphasized the discordance between temperature records, taken from high altitude and breezy weather stations, and bodily experience of heat waves on New York streets. In a series of illustrations and an article, the magazine effectively illustrated the urban heat island. In the first of two illustrations, setting the scene in the Weather Station, breezes from the harbor were exaggerated as freezing wind currents and icicles; station employees dressed in the gear of the famous Antarctic explorers of the early 1900s. The data scientists wore windproof canvas smocks, gloves, and headgear, including goggles. Icicles grew from their beards. A radiator steamed near the window, but it couldn’t check the room’s cold.

The accompanying article decried the station forecaster as out of touch due to “the cool temperature of his perch” and westerly breezes stirring his papers, in contrast to the urban masses who “swelter[ed] and boil[ed] down here on the ground, cooked by the heat of sizzling pavements and gigantic walls of steel and stone!”14 In the bottom illustration, the men in front of the Weather Station sweated through wilted collars and removed their hats and jackets. Hair styles fell flat and stuck to sweaty foreheads. To illustrate heated air, the artist played up bodily response and emotions. The crowd was uniformly wide-eyed, dazed by the temperature. A few men gestured angrily at the mockingly titled “false prophets” above. Some carried thermometers that challenged the official posted high of 90°F; the extreme heat burst one thermometer, its mercury dripping to the pavement.

The article and illustrations undermined meteorologists’ expertise, declaring expert knowledge useless, even disingenuous, in the face of bodily experience. The author offered a humorous imaginary confrontation between the frozen forecasters and the masses: “[s]ee here…what the dickens do you mean, giving us…your ding-danged old air-cooled temperature…Is that fair? Is that honest?… that’s the temperature we’re living and working and dying in, isn’t it?”15

“Given the global urbanization and rising temperatures of the twenty-first century planet, extreme heat is a mounting problem for urban areas, an environmental challenge that minority and poor communities unequally shoulder.”

As Harper’s reminded its readers in 1911, heat is a meteorological event but it cannot be fully assessed without reference to human experiences. Given the global urbanization and rising temperatures of the twenty-first century, extreme heat is a mounting problem for urban areas, an environmental challenge that minority and poor communities unequally shoulder.16 Heat waves exacerbate the anthropogenic environmental challenges of New York’s urban heat island. The urban fabric remains a determining force in the environmental challenges of summer in the city. The history of urban heat waves is a history of record-breaking highs but also of sweaty, sticky, corporeal experiences. It is a reminder that despite the mid-twentieth century rise of air-conditioning that elided this relationship for some, the body and environment—manifest as summer weather—are always imbricated.

Notes
  1. Donald M. Yow, Urban Heat Islands: Observations, Impacts, and Adaptation,” Geography Compass 1 no. 6 (2007): 1227–1251.
  2. Julian Ralph, “A Hot Night in New York,” Harper’s (August 17, 1889): 667.
  3. Luke Howard, The Climate of London: Deduced from Meteorological Observations, Made at Different Places in the Neighbourhood of the Metropolis, vol. 1 (London: W. Phillips, 1818); Helmet E. Landsberg, The Urban Climate (New York: The Academic Press, 1981); and Gerald Mills, “Luke Howard and The Climate of London” Weather 63, no. 6 (June 2008), 155.
  4. “Shade-Trees as Disinfectants,” New York Times (Apr. 7, 1873): 4.
  5. Stephen Smith, “Vegetation a Remedy for the Summer Heat of Cities,” Appletons’ Popular Science Monthly (Feb. 1899), 440.
  6. “The Intemperate Zone” Harper’s (August 10, 1878): 626-627.
  7. “Central Park Heat Wave Climatology,” National Weather Service https://www.weather.gov/okx/nycheatwave (accessed 2 April 2020).
  8. Ralph, “A Hot Night.”
  9. Alvin T. Burrows, “Hot Waves: Conditions Which Produce Them, and Their Effect on Agriculture,” Yearbook of the U. S. Department of Agriculture 22 (1900): 325-336.
  10. Peter J. Robinson, “On the Definition of a Heat Wave,” Journal of Applied Meteorology 40 (April 2001), 762. 
  11. Smith, “Vegetation a Remedy,” 437. For an overview of body temperature and perspiration from New York State public health officials see New York (State) Commission on Ventilation, Ventilation; Report of the New York State Commission on Ventilation (New York: E.P. Dutton & Co., 1923), 59-60.
  12. “Excessive Heat Conditions,” National Weather Service, https://www.weather.gov/phi/heatcond (accessed 2 April 2020); Krzysztof Błażejczyk et. al., “An Introduction to the Universal Thermal Climate Index (UTCI),” Geographic Polonica 86 iss. 1 (2013): 5-10; and Robinson, “On the Definition of a Heat Wave,” 762-3.
  13. “The Recent Heat Wave,” Scientific American (August 22, 1896), 166.
  14. William Inglis, “The Thermometer and the Weather Bureau,” Harper’s (August 19, 1911): 13-14.
  15. Inglis, “The Thermometer and the Weather Bureau.”
  16. Henry Fountain, “North America Has Its Hottest June on Record,” New York Times (July 7, 2021) https://www.nytimes.com/2021/07/07/climate/climate-change-temperatures-june.html?smtyp=cur&smid=tw-nytclimate (accessed July 8, 2021); Rachel Frazin and Zack Budryk “Scientists warn of climate change intensifying heat waves,” The Hill (June 30, 2021) https://thehill.com/policy/equilibrium-sustainability/560836-scientists-warn-of-climate-change-intensifying-heat-waves?rl=1 (accessed July 8, 2021), and Brad Plumer, Nadja Popovich and Brian Palmer “How Decades of Racist Housing Policy Left Neighborhoods Sweltering,” New York Times (August 24, 2020) https://www.nytimes.com/interactive/2020/08/24/climate/racism-redlining-cities-global-warming.html (accessed July 8, 2021).
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Kara Murphy Schlichting

Kara Murphy Schlichting is an Associate Professor of History at Queens College, CUNY. Schlichting has published in the Journal of Urban History and the Journal of Planning History. She is a co-editor of H-Environment Roundtables and the author of 'New York Recentered: Building the Metropolis from the Shore' (University of Chicago Press 2019).

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