page_title: 1966 New York City smog
section_title: November 19–23: stagnant air traps pollutants
hierarchical_section_title: 1966 New York City smog / Timeline of smog event / November 19–23: stagnant air traps pollutants
caption_attribution_description: English: Weather maps depicting wind patterns at a height of 18,000 feet from November 21–26, 1966, created by employees of the US Department of Health, Education, and Welfare.
context_page_description: The 1966 New York City smog was a major air-pollution episode, during which the city's air became filled with damaging levels of several toxic pollutants. Smog covered the city and its surrounding area from November 23 to 26, coinciding with that year's Thanksgiving holiday weekend. It was the third major smog in New York City, following events of similar scale in 1953 and 1963.
  On November 23, a large mass of stagnant air over the East Coast trapped pollutants in the city's air. For three days, New York City was engulfed in dangerously high levels of carbon monoxide, sulfur dioxide, smoke, and haze. Pockets of air pollution pervaded the greater New York metropolitan area, including parts of New Jersey and Connecticut. By November 25, the smog became severe enough that regional leaders announced a "first-stage alert". During the alert, leaders of local and state governments asked residents and industry to take voluntary steps to minimize emissions. Health officials advised people with respiratory or heart conditions to remain indoors. The city shut off garbage incinerators, requiring massive hauling of garbage to landfills.
context_section_description: In November 1966, New York City was experiencing an unseasonably warm "Indian summer". A cold front from Canada brought clean air to the city on November 19, but the cold front was held in place by pressure from the higher atmosphere. An anticyclonic temperature inversion—in other words, a warm, mostly stationary air mass located atop a cooler air mass—formed over the East Coast on November 20.
  Unlike atmospheric convection—the ordinary process of lower, warm air rising—inversions leave cooler air suspended below warm air, preventing the lower air from rising and trapping airborne pollutants that would ordinarily disperse in the atmosphere. Such weather events are common, but they are usually followed by a strong cold front that brings an influx of clean air and disperses pollutants before they have enough time to become highly concentrated; in this case, a cold front approaching west through southern Canada was delayed. When explained in less formal terms, the process of an inversion causing a smog event has been compared to a lid that holds in pollutants or a balloon that fills with pollutants. In general, smog events occur not because of a sudden increase in a region's output of pollution, but rather because weather conditions like stagnant air prevent the dispersal of pollutants that were already present.
  The inversion prevented air pollutants from rising, thereby trapping them within the city. The smog event itself started on Wednesday November 23, coinciding with the beginning of the long Thanksgiving weekend. The material sources of the smog were particulates and chemicals from factories, chimneys, and vehicles. Sulfur dioxide levels rose and smoke shade—a measure of visibility interference in the atmosphere—was two to three times higher than usual.
caption: These weather maps show winds at 18,000 feet from November 21–26, 1966. A mass of warm air spreading east and south above the East Coast created the inversion that trapped pollutants near the ground.[48]
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