Phoenix heat wave could be the most intense on record for the city
The Valley of the Sun has seen temperatures of 110 degrees or above for nearly a month now, and AccuWeather forecasters now say this could make it the most intense heat wave the city has experienced since records began.
AccuWeather Chief Meteorologist Jon Porter explains how the boom in the Phoenix metro population has effected the temperature over the years.
Geneva Seitz was used to cold winters in the suburbs of Philadelphia that forced her to stay inside. Now, after moving to Scottsdale, a suburb of Phoenix, at the beginning of 2023, the summers are too hot for her to spend too long outdoors.
The heat wave brought more changes, including getting up earlier on the weekends if she and her family wanted to spend time outside. If someone in the home needs to use the oven or the dryer, they have to avoid using them in the peak hours of the afternoon, which can make it difficult to cool the apartment.
The ongoing heat wave in Phoenix has been the most intense one the city has experienced since records began in 1895, according to the AccuWeather HeatWave Counter and Severity Index™. This index takes into account the number of days a heat wave lasts along with how high temperatures climb during the hot spell.
A person tries to cool off in the shade Tuesday, July 18, 2023, in Phoenix. (AP Photo/Ross D. Franklin)
The Valley of the Sun has sweltered under temperatures of 110 degrees Fahrenheit or higher for 25 consecutive days and counting. The old record streak of 18 days at or above a high temperature of 110 degrees, set in 1974, was broken Tuesday, July 18, when temperatures met the benchmark around noon -- but it wasn't the last record to fall.
Several daily high-temperature records were obliterated by the scorching heat, as well as records for the highest daily low temperature. On Wednesday, July 19, the mercury only dropped to 97 degrees, breaking the all-time record warm low of 96 degrees set on July 15, 2003. By July 22, the Valley of the Sun had seen 13 consecutive days with daily lows at 90 degrees or higher. As of the morning hours on July 25, the temperature had not dipped below 90 for 16 nights in a row.
"This really stands out on the new exclusive AccuWeather HeatWave Counter and Severity Index™, which quantifies and measures the duration and intensity of heat," AccuWeather Chief Meteorologist Jonathan Porter said.
Through July 20, the combination of temperatures consistently rising to or above 110 degrees for 21 days led to a Heat Wave Index sum of 65.
"That's almost two times as intense as the number two heat wave," Porter said.
The second most intense heat wave Phoenix experienced on record lasted 17 days from late July of 1995 to mid-August. Its Heat Wave Index sum was 36.
On the hottest day of that stretch in 1995, the mercury reached 118 degrees Fahrenheit on July 27. The lowest high temperature of the stretch came a day later when the mercury "only" hit 109 degrees, according to AccuWeather Senior Meteorologist John Gresiak.
In this recent heat wave, July 19 and July 20 have been the hottest days in the stretch, the mercury reaching 119 degrees. The lowest daily high temperatures during this streak were recorded on July 11 and July 12 when temperatures reached 111 degrees.
Since July 20 through Sunday, July 22, 10 more digits have been added to the Heat Wave Index sum, making the total 75 so far.
"Based on the forecast through Saturday, Aug. 5, an additional 12 digits will be added to the Heat Wave Severity Index, pushing the total for the stretch to 87," AccuWeather Director of Forecasting Operations Dan DePodwin said.
Heat is the number one weather-related cause of death in the U.S., outpacing tornadoes, floods and even hurricanes. This season, there have been 12 confirmed heat-associated deaths in Maricopa County, where Phoenix is located, according to the county's department of public health. Another 55 deaths remain under investigation. Last year, 17 heat-related deaths had been confirmed and 126 remain under investigation.
The number of people at risk of heat events in Phoenix continues to grow as the population booms. More people are moving to Maricopa County than anywhere else in the country, according to data from the Census Bureau. The large majority of that growth is funneled into the Phoenix metro area.
In 2012, about 4.2 million people lived in the area. About a decade later, the population surpassed 5 million for the first time, according to the U.S. Census.
Once a resident of Pennsylvania, Seitz told AccuWeather she and her family have had to make adjustments with the shift from the Northeast to the Desert Southwest.
"We were used to very cold winters that we would spend mostly indoors, that has now shifted to the very hot summers that we are not going outdoors," Seitz said. "We had never been somewhere this hot, so it has been an adjustment, learning all the tricks like always remembering the sun visor in the car or wearing long sleeves when hiking. Our neighbors have been very helpful, teaching all the tricks for living in Arizona in the summer."
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