What is a Heat Wave?

What exactly is a heat wave and why can it be dangerous?

In the United States, to be considered an official heat wave…
The air temperature must reach 90°+ at a location for three or more consecutive days. 

Some parts of the United States commonly reach 90° or higher. In Connecticut, Windsor Locks averages 18 days of 90°+ temperatures each year. The shoreline* averages closer to 6 days of 90°+ temperatures per year, but that varies depending on the wind direction, as sea-breezes can keep conditions cooler. (*Shoreline average is for Stratford/Sikorsky Airport)

Why 90°F?
Well, even if there is little to no humidity, once the air temperature exceeds 90°, there is an increased “likelihood of heat disorders with prolonged exposure or strenuous activity.” The “heat index” is a factor of heat and humidity. As conditions get more humid, the heat index rises above the actual air temperature. Once the heat index reaches 105°, conditions are considered dangerous. Extreme danger sets in at heat indicies above 125°.

The National Weather Service (NWS) says, “During extremely hot and humid weather the body’s ability to cool itself is affected. When the body heats too rapidly to cool itself properly, or when too much fluid or salt is lost through dehydration or sweating, body temperature rises and heat-related illnesses may develop.

  • Heat-related illnesses can range from heat cramps to heat exhaustion to more serious heat stroke. Heat stroke can result in death and requires immediate medical attention.
  • Factors or conditions that can make some people more susceptible to heat-related illnesses include age (older adults and young children), obesity, fever, heart disease, mental illness, poor circulation, prescription drug and alcohol use, and sunburn. Sunburn, caused by ultraviolet radiation from the sun, can significantly retard the skin’s ability to shed excess heat.”

The NWS will issue Heat Advisories and Excessive Heat Watches and Warnings when they expect dangerously hot conditions. These statements should be taken seriously, as prolonged exposure to extreme heat can be dangerous to the human body. Don’t forget pets too, as the heat can be just as dangerous to them, if not worse. Never leave pets unattended in cars and make sure that pets can stay in air conditioned spaces during hot weather with plenty of water to drink. The same goes for children, the elderly and disabled adults.

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Quincy is a meteorologist and storm chaser who travels around the country documenting and researching severe weather. He has on-air experience with stations such as WTNH-TV in New Haven, CT and WREX-TV in Rockford, IL. He was most recently a digital meteorologist for weather.com. After achieving his B.S. degree in Meteorology at Western Connecticut State University (WCSU) in 2009, he returned as a University Assistant to help produce weather broadcasts. He also gave guest lectures and worked on website design. He has over nine years of professional weather forecasting experience and his forecasts have been featured in newspapers and on radio stations in multiple states.

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