Feature Photo: Ron Adar / Shutterstock.com
Extreme heat has always been one of New York City’s most dangerous weather threats. Unlike a blizzard or hurricane, a heat wave can leave few dramatic photographs of destruction while quietly driving mortality higher across apartments, tenements, workplaces, streets, and neighborhoods. Before residential air conditioning became common, the danger was even greater. Families slept on rooftops, fire escapes, piers, beaches, and park lawns in search of moving air, while horses, transit systems, electrical networks, and water supplies struggled under the same conditions.
Comparing historic heat waves is complicated because New York did not always count heat deaths in the same way. Some historical figures represent deaths officially attributed to heat, while others represent excess mortality—the number of deaths above what would normally have been expected during the same period. For that reason, this list is arranged chronologically rather than pretending that every event can be ranked with perfect numerical precision. These are ten of the deadliest, longest, hottest, and most consequential heat waves documented in New York City history.
1. The Great Heat Wave of August 1896
Dates: August 4–13, 1896
Central Park: Ten consecutive days of 90-degree-or-higher temperatures
Estimated toll: As many as 1,500 excess deaths in New York City
The August 1896 heat wave remains one of the darkest weather disasters in New York history. For ten consecutive days, Central Park recorded temperatures of at least 90 degrees. The larger danger came from the combination of heat, humidity, stagnant air, overcrowded housing, and the inability of apartments to cool after sunset.
In crowded tenement neighborhoods, residents searched desperately for relief. People slept on rooftops, fire escapes, stoops, and piers. Horses died by the hundreds, creating a sanitation crisis on streets that still depended heavily on animal transportation.
Historian Edward P. Kohn, writing for the New York State Archives, compared deaths in Manhattan and Brooklyn during the ten-day period with the same dates in 1895 and concluded that the heat may have caused as many as 1,500 fatalities. Modern public-health research continues to cite the 1896 event as an example of the enormous mortality New York once suffered during extreme heat.
The heat wave also became part of Theodore Roosevelt’s New York story. Roosevelt was president of the Board of Police Commissioners at the time and pushed police officers to help distribute ice to poor neighborhoods. The city’s broader response was limited by modern standards, but the disaster helped expose how deadly overcrowded housing could become during prolonged summer heat.
2. The Great Heat Wave of 1901
Dates: June 26–July 3, 1901
Central Park peak: 100°F on July 1 and July 2
Reported toll: Approximately 600 deaths were already being reported across Greater New York by July 4
The heat returned with devastating force in 1901. Central Park recorded eight consecutive days of at least 90 degrees from June 26 through July 3, including back-to-back 100-degree days on July 1 and July 2.
Contemporary newspaper reports described people collapsing throughout the city and tenement residents carrying mattresses outdoors in hopes of finding cooler air. By the early hours of July 4, newspapers were reporting an estimated 600 heat deaths across Greater New York during the preceding six days.
Later scientific research examining New York heat and mortality from 1900 onward identified the 1901 heat wave as the deadliest event in the study period. That distinction is important because it demonstrates how dangerous extreme heat remained even after the catastrophe of 1896 had supposedly shown the city what could happen.
3. The July 1911 Heat Wave
Dates: Early to mid-July 1911
Reported toll: About 158 deaths in New York City
The northeastern heat wave of 1911 became another major urban disaster. New York City never needed an all-time record temperature for the event to become deadly. Humidity, warm nights, crowded housing, and a long stretch of oppressive weather were enough.
Historical accounts place the New York City death toll at approximately 158 people, with hundreds of horses also dying. Families escaped apartments for parks, beaches, rooftops, piers, and any other place where they could find moving air.
The 1911 crisis is an important reminder that the danger of a heat wave cannot be measured by the afternoon high temperature alone. When nights remain hot and buildings retain the previous day’s heat, the human body loses its chance to recover.
4. New York’s Record Heat of July 1936
Dates: July 7–15, 1936, with the worst heat on July 8–10
Central Park peak: 106°F on July 9, 1936
The summer of 1936 produced one of the most extraordinary heat events in North American history. In New York City, the defining number is 106 degrees. Central Park reached that temperature on July 9, 1936, establishing the city’s all-time official high-temperature record. That record still stands.
The following day reached 102 degrees. The extreme temperatures came during the Great Depression, when residential air conditioning was virtually nonexistent and millions of New Yorkers relied on open windows, fans, fire hydrants, swimming pools, beaches, movie theaters, and public spaces for relief.
The 1936 event is sometimes assigned a precise New York City death toll in popular summaries, but the historical record does not support a single universally accepted citywide figure comparable to the better-documented 1896 or 1966 excess-mortality estimates. Its place on this list rests instead on its exceptional temperature, documented mortality impact, and its status as the hottest official day ever recorded in Central Park.
5. The 12-Day Heat Wave of 1953
Dates: August 24–September 4, 1953
Central Park peak: 102°F on September 2
Duration: Twelve consecutive days of 90-degree-or-higher temperatures
New York’s 1953 heat wave holds a record of a different kind. From August 24 through September 4, Central Park recorded twelve consecutive days with temperatures of at least 90 degrees, the longest such streak in the city’s official weather record.
The sequence was relentless: 91, 91, 91, 94, 98, 99, 98, 100, 97, 102, 94, and 90 degrees. The 102-degree reading on September 2 is also the most recent time Central Park has reached 100 degrees during the month of September.
Photographs from the summer show New Yorkers using familiar methods of urban survival: open fire hydrants, crowded swimming areas, ice, fountains, and waterfronts. Air conditioning existed, but it was still far from universal in homes. The length of the event made it particularly dangerous because residents endured day after day with limited nighttime recovery.
6. The Deadly Heat Wave of July 1966
Dates: July 2–15, 1966
Central Park peaks: 100°F on July 2, 103°F on July 3, and 101°F on July 13
Estimated toll: Approximately 1,181 excess deaths in New York City
The July 1966 heat wave is one of the most important events in the history of heat mortality in New York because researchers later studied it in detail. A major epidemiological analysis defined the New York heat episode as a fourteen-day period from July 2 through July 15, during which twelve days reached at least 90 degrees.
Researchers estimated approximately 1,181 excess deaths in New York City during the episode, representing a 36 percent increase over expected mortality. People over age sixty-five and residents of low-income, crowded, and poor-quality housing faced especially high risk.
Only a small portion of the deaths were necessarily recorded on death certificates as having been caused directly by heat. Many were deaths in which extreme temperature worsened cardiovascular, respiratory, circulatory, or other underlying illnesses. That distinction would become increasingly important in the way public-health officials measured heat mortality.
7. The July 1977 Heat Wave and Blackout
Dates: July 13–21, 1977
Central Park peak: 104°F on July 21
Duration: Nine consecutive days of at least 90 degrees
The heat wave of July 1977 is inseparable from one of the most infamous nights in New York City history. On July 13, electrical failures following lightning strikes and cascading problems in the regional power system produced the 1977 New York City blackout.
The blackout did not cause the heat wave, and the heat wave itself was not the sole cause of the electrical collapse. However, the city was already under heavy summer electrical demand, and losing power during hot, humid weather made conditions far more dangerous for residents who depended on fans, elevators, water pumps, and air conditioning.
The heat intensified after power was restored. Central Park reached 100 degrees on July 18, 102 on July 19, and 104 on July 21. A later public-health study found a clear relationship between very hot days and elevated mortality during the period, although it did not isolate a simple death count that could be attributed solely to the blackout.
8. The Repeated Heat Waves of July 1999
Major events: Several heat waves during July 1999, including an eleven-day stretch from July 23–August 2
Early-July peak: 101°F
Documented toll: At least 27 heat-related deaths during the earlier July heat waves
The summer of 1999 demonstrated that New York remained vulnerable even after air conditioning had become common. The city endured repeated heat waves during July, and at least twenty-seven heat-related deaths were attributed to the earlier episodes that month.
One early-July heat wave also coincided with an eighteen-hour power failure in Washington Heights and Inwood that left a large section of Upper Manhattan without electricity during extreme heat.
Later in the month, Central Park began an eleven-day run of temperatures at or above 90 degrees from July 23 through August 2. At the time, it was the second-longest official heat wave in New York City history, behind only the twelve-day event of 1953.
9. The 2006 Heat Wave and Queens Power Crisis
Heat-wave dates: July 27–August 5, 2006
Heat index: Above 100°F on three days
Documented mortality: 46 confirmed heat-stroke deaths, plus approximately 100 excess deaths associated with the heat wave
The summer of 2006 became a turning point in modern New York heat planning. A severe ten-day heat wave ran from July 27 through August 5. The maximum heat index exceeded 90 degrees throughout the event and passed 100 degrees on three days.
New York City recorded forty-six confirmed heat-stroke deaths associated with the 2006 heat waves. Public-health analysis also found approximately one hundred excess deaths from natural causes during the July 27–August 5 event, demonstrating again that death certificates alone can dramatically understate the true impact of extreme heat.
The crisis followed a major power failure in western Queens that began on July 17. The outage affected communities including Astoria, Long Island City, Sunnyside, and Woodside and left many residents and businesses without reliable electricity for more than a week. The outage and the subsequent heat emergency became powerful reminders of how electrical infrastructure and public health can intersect during a New York summer.
10. The Record-Breaking Heat Wave of July 2011
Dates: July 21–24, 2011
Central Park peak: 104°F on July 22
Documented toll: At least 19 deaths in New York City
The July 2011 heat wave brought New York back to temperatures rarely seen in the modern city. Central Park reached 104 degrees on July 22, one of the highest official readings in New York history. The heat index climbed to approximately 114 degrees in Central Park during the worst of the event.
New York City’s hazard records attribute at least nineteen deaths in the five boroughs to the episode: seven in Brooklyn, six in the Bronx, four in Manhattan, and two in Queens.
The event took place in a city far better prepared for extreme heat than New York had been in 1896 or 1966. Cooling centers, emergency alerts, air conditioning, targeted outreach, and modern medical care had greatly reduced the risk. Even so, the deaths showed that extreme heat remained capable of killing vulnerable New Yorkers despite more than a century of adaptation.
What New York Has Learned About Heat
The history of these heat waves reveals one of the most important changes in New York public health: officials now understand that direct heat-stroke deaths tell only part of the story. Heat can worsen heart disease, respiratory illness, diabetes, and other medical conditions, producing deaths that may never be labeled “heat stroke” on a death certificate.
In its 2026 Heat-Related Mortality Report, the New York City Health Department estimated that approximately 500 New Yorkers now die from heat-related causes in an average year. Most are heat-exacerbated deaths rather than deaths directly coded as heat stress.
New York is also getting warmer. The city’s dense concentration of buildings and pavement intensifies the urban heat-island effect, and climate change is increasing the frequency and duration of dangerous hot weather. Cooling centers, air conditioning, tree cover, access to water, reliable electricity, and checking on vulnerable neighbors have therefore become part of the city’s modern heat-response strategy.
Extreme heat can be life-threatening. During a heat emergency, follow current New York City guidance, stay hydrated, limit strenuous outdoor activity, use air conditioning or a cooling center when needed, and check on older adults and people with chronic medical conditions. Anyone experiencing signs of heat stroke—including confusion, loss of consciousness, or dangerously high body temperature—needs emergency medical attention.
Summary of Historic New York City Heat Waves
| Year | Key Dates | Peak / Duration | Documented Impact |
|---|---|---|---|
| 1896 | Aug. 4–13 | 10 straight 90°F+ days | As many as 1,500 excess deaths |
| 1901 | Jun. 26–Jul. 3 | 100°F; 8 straight 90°F+ days | About 600 deaths reported by July 4 |
| 1911 | Early–mid July | Prolonged humid heat | About 158 NYC deaths reported |
| 1936 | Jul. 7–15 | 106°F on Jul. 9 | NYC all-time official temperature record |
| 1953 | Aug. 24–Sep. 4 | 12 straight 90°F+ days; 102°F | Longest official NYC heat wave |
| 1966 | Jul. 2–15 | 103°F peak | About 1,181 excess deaths estimated |
| 1977 | Jul. 13–21 | 104°F; 9 straight 90°F+ days | Heat coincided with historic blackout; mortality increased on hottest days |
| 1999 | Multiple July events | 11-day late-July heat wave | At least 27 heat-related deaths in earlier July waves |
| 2006 | Jul. 27–Aug. 5 | Heat index above 100°F on 3 days | 46 confirmed heat-stroke deaths plus about 100 excess deaths |
| 2011 | Jul. 21–24 | 104°F on Jul. 22 | At least 19 NYC deaths |
For more stories about how New Yorkers have endured major citywide emergencies, readers can explore the history of New York City’s great blackouts, the history of Central Park, the history of Brooklyn’s Prospect Park, and our look at New York City’s water and the Catskill Aqueduct.
Sources
National Weather Service — New York City Heat Waves
National Weather Service — 100-Degree Days in Central Park
New York State Archives Partnership Trust — The Scourge of Summer
Epidemiology — Heat and Mortality in New York City Since the Beginning of the 20th Century
Environmental Research — Patterns of Urban Heat-Wave Deaths in New York City, July 1966
Public Health Reports — Public Health Concerns Associated With the New York City Blackout of 1977
Centers for Disease Control and Prevention — Heat Illness and Deaths, New York City, 2000–2011
NOAA Climate.gov — Protecting People From Sweltering City Summers
New York City Health Department — 2026 Heat-Related Mortality Report
Updated August 31, 2026.
