NYC could see its first heat wave of 2025. Here's what that means.
Temperatures are expected to climb into the 90s Sunday and then stay there for a few days. Here's everything to know about heat waves in the city and other heat related terms.
What is a heat wave?
CBS News New York
While New York City is no stranger to hot days, it's when those hot days become incessant and successive that problems start to arise. When high temperatures reach or exceed 90 degrees for three consecutive days or more, that is defined as a heat wave. On average, the city sees two heat waves per summer, lasting around four days each. The longest heat wave ever recorded in the city lasted 12 days in 1953 from Aug. 24 to Sept. 4. In a typical summer, a high temperature of 90 degrees or above occurs 15 times. In 2024, 21 of them were recorded. Climate projections indicate that this number may rise to 69 by the 2050s, with the duration increasing to six days.
CBS News New York
It's during these prolonged periods of heat that the most heat related illnesses and deaths occur. In fact, 370 deaths are attributed to heat each year in the city, with most of them happening during heat waves. Heat is also the number one weather related killer across the country. Neighborhoods in the South Bronx, Upper Manhattan, and Central Brooklyn are the most susceptible due to a variety of factors including socioeconomic status, higher rates of pollution, lack of air conditioning and less trees. Elderly people are most at risk, regardless of any of these factors.
Exacerbating the effects of heat waves in the city is the city's infrastructure. The concrete jungle, filled with towering buildings and endless paved surfaces allows for more efficient heating during the daytime due to a phenomenon known as the 'Urban Heat Island Effect". However, the effects of this phenomenon are most pronounced at night. This is because the infrastructure of the city traps in all of the heat that built up during the day, thus preventing a normal nocturnal cooldown seen in non-urban settings. Some nights there can be as much as a 20-degree difference in temperature between the city and surrounding suburbs. High heat during the day is stressful enough on the human body, but when it can't cool down even at night, that becomes a major health concern.
Heat wave vs. heat dome
CBS News New York
Many times, heatwaves are the direct result of the meteorological phenomenon known as a "Heat Dome." Heat Domes are areas of very strong high pressure that set up over a particular region and become basically stationary. From their stationary location, they are able to pump very hot air and humidity to areas within their vicinity, which can be quite extensive at times. Since they don't move much, air within them can become extremely hot and stagnant, leading to dangerously high temperatures and poor air quality. Heat Domes can last anywhere from a few days to several weeks before breaking down.
Excessive heat warning & heat advisory
CBS News New York
Although not always the case, excessive heat warnings usually coincide with heat waves. Excessive heat warnings are issued 24 hours in advance of a forecasted heat index of at least 105 degrees or above for at least two consecutive hours. High heat indices are usually associated with higher levels of humidity, and New York City certainly sees a lot of that during the summer, especially during the month of August. The high levels of humidity work in conjunction with the Urban Heat Island Effect to produce higher heat indices.
Excessive heat warnings are the highest form of heat alerts that are issued. They are not issued as regularly as heat advisories, being reserved for only the most sweltering days. An average summer typically yields between one to three of these such warnings. Some summers have none, such as in 2022, while others have much more.
CBS News New York
When an excessive heat warning is issued, extreme caution is needed. This includes limiting time outdoors, drinking plenty of water, not drinking too much alcohol or coffee, exercising during cooler portions of day, eating light meals and staying in air-conditioned places.
CLICK HERE to find a cooling center in New York City.
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