Phoenix Sets National Record for Duration of Heat Wave

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July 19, 2023 – The city of Phoenix set a pair of heat records on Tuesday and is on track for a third record today.

The temperature at Phoenix Sky Harbor Airport hit a record 118 degrees Fahrenheit, topping the previous record for the day of 115 degrees set in 1989. The normal temperature for the day is 107 degrees, according to the city’s National Weather Service office.

The soaring mercury also landed the city’s hot streak in the record books. Tuesday marked the 19th straight day that the temperature reached 110 degrees or higher at the airport, breaking the 1974 record of 18 days. That’s also a national record. Among the 25 most populous U.S. cities, none has had such a long stretch of 110-degree days.

Phoenix has charted 22 days this year of temperatures reaching 110 degrees or higher, with several more forecasted. The city usually averages 21 days annually of temperatures at 110 degrees or higher.

Another new record looked likely this morning, the weather service tweeted, because the morning low temperature of 97 degrees would be the warmest low temperature ever recorded in the city.

The lack of relief from warm temperatures overnight is hard on people’s bodies, which need a break from the heat in order to function properly, said Lara Cushing, PhD, an assistant professor of environmental health sciences at The California State University.

"From studying extreme heat events, we know that health effects are worse if heat persists overnight," Cushing said in an article about hot nights on the university’s website. "The body tries to maintain a relatively constant temperature within a range, and being exposed to heat for prolonged periods makes that difficult." 

While healthy people are vulnerable to heat stress during an extreme heat event such as the one gripping a huge swath of the U.S. right now, those who are sick or have certain conditions are particularly at risk. 

“People with certain preexisting illnesses such as a heart condition or kidney issues are even more vulnerable,” Cushing said. “And the elderly who live alone and pregnant women are vulnerable — their thermoregulatory systems are often not as able to cool the body."