Phoenix Shatters Heat Record With 100 Consecutive Days Above 100 Degrees

Phoenix, Arizona, is the nation’s fifth largest city, with roughly five million people living in its metro region. But as it’s located in the desert Southwest, it’s also one of the hottest. This summer, Phoenix has shattered heat records, surpassing 100 straight days with temperatures above 100 degrees Fahrenheit.

“For most of the state, it’s looking like the hottest summer on record,” Sean Benedict, the lead meteorologist at the National Weather Service in Phoenix, tells the Arizona Republic’s Hayleigh Evans.

The current hot streak began on May 27, and meteorologists say the forecast isn’t showing any relief. The previous record for consecutive 100-degree days in Phoenix was set in 1993, at 76 days. While this summer didn’t quite reach the extreme high temperatures of last year, which repeatedly neared 120 degrees, the overall average from the sustained heat is higher this year by nearly two degrees, at 98.9 degrees Fahrenheit.

“That’s incredible, just to think of the average temperature that we’re living in here in Phoenix,” Matt Salerno, a meteorologist at the National Weather Service’s Phoenix office, says to Scientific American’s Andrea Thompson.

Phoenix’s extreme heat is occurring due the conflux of major weather patterns and trends in global climate change. Each summer, the North American Monsoon descends on the American Southwest—including Arizona. For most of the year, the dominant winds in Arizona come from the west, blowing in dry air and clear skies. But those winds shift during summer, when southerly breezes can bring moisture to the desert. The result is sudden and spectacular thunderstorms, often during the peak heat of the day.

This year in Phoenix, though, the heavy rains failed to materialize. “The problem is that we’ve had a drier-than-normal monsoon season here in Phoenix,” Gabriel Lojero, a meteorologist with the National Weather Service in Phoenix, tells the New York Times’ Derrick Bryson Taylor. “At times during the summer months, we do depend on days where you have a lot of clouds, or it’s rain, and so, your temperatures tend to cool down somewhat.”

The lack of monsoon clouds has been compounded by a series of heat domes that have settled over the region. These weather features are becoming increasingly common as the climate warms.

“I would like the public to understand that this heat is no longer a rare occurrence,” Juan Declet-Barreto, a social scientist at the Union of Concerned Scientists, says to the Guardian’s Aliya Uteuova. “It will continue to get worse year after year if we don’t make drastic emissions reductions. We need to decarbonize our energy, industrial, agricultural and transportation sectors. There’s no way around that if we want cities like Phoenix to be livable.”

As Muntu Davis, a health officer for Los Angeles County in California, tells David Brandt of the Associated Press, this isn’t an exaggeration: “Hot days aren’t just uncomfortable—they can be dangerous.”

In Maricopa County, which contains Phoenix, at least 645 people died of heat-related illness last year. Through August 31 of this year, the county has confirmed 177 heat-related deaths.

While the extreme daily high temperatures get most of the attention, weather experts say the nightly low temperatures are also important, since the human body needs low temperatures at night to cool off and recover from the day.

The average overnight low in Phoenix this year has been 87.5 degrees, and for 37 nights, the low didn’t drop below 90 degrees. “Our low temperatures are most places’ high temperatures,” Salerno tells Scientific American.

Community resources like cooling, shade and hydration stations can help alleviate the risk of heat-related deaths amid the high temperatures, which appear to be here to stay: Despite the arrival of September, the forecast is showing no signs of relief. Benedict tells the Arizona Republic that the next week or two will continue to reach upward of 110 degrees. And it’s likely to stay above 100 into October, extending the margin of the city’s new heat record.

“The morning lows should be a little bit better, but overall, the odds are tilted towards an above-normal fall,” Benedict adds.