Relentless heat, hot Phoenix nights raise risk of another record-breaking year for deaths

Phoenix has entered the deadly hot phase of summer, when sustained daytime temperatures stress bodies and simmering nights offer little relief.

Climate warming and urban magnification of heat have led to nighttime lows that hover around 90 degrees, presenting a danger to both those experiencing homelessness and those who can’t or don’t cool their homes. Experts advise that it’s a time for those at risk to seek out cooling centers, though most are not open at night.

Even after a dozen days at or above 110 degrees, “the exclamation point on this event is yet to come,” said Phoenix Heat Response and Mitigation Director David Hondula.

That’s because still hotter days, with highs reaching perhaps 118 degrees, are in the forecast for the weekend and beyond. Those days will carry with them hot nights that cause cumulative stress on people who can’t escape the heat.

“The lack of respite during this whole event has been a concern,” Hondula said.

His office and others have joined volunteers in focusing on the unsheltered population, getting people water and information about where to go, he said.

Heat deaths take a toll among unsheltered people

Though always hot in summer, Phoenix in recent years has experienced a worsening heat crisis that often reaches a peak in July. Maricopa County counted 425 heat-related deaths last year, a 25% increase from 2021, and saw a spike when, as now, daytime highs peaked above 110 and nighttime lows lingered around 90.

July 15 was last year’s hottest day, at 115 degrees, and 10 people died then. The county’s death reports lag, and Hondula said it’s too early to compare this summer’s numbers. This year, the temperature reached 116 degrees on July 3.

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With 245 deaths last year, Phoenix far outpaced the next deadliest city, Mesa, which recorded 36. The largest cluster was in the Phoenix neighborhood surrounding “The Zone,” with encampments of unsheltered people. The Maricopa County Public Health Department’s report considered 178 of the 425 countywide victims to be people who were homeless.

But 51 of last year’s victims died indoors in places with air conditioners that were not functioning at the time, while three had no electricity to power their units. Fifteen of them died indoors but had no air conditioning units.

For people in that situation, or with no shelter, a network of cooling centers including libraries, Salvation Army sites and others can be lifesavers, though many close even before the heat of the day has passed. Hondula said he expects some will extend their hours and remain open on the weekend. In the home, he suggested, people should shade their windows during the day to reduce heat accumulation.

Phoenix is also working to add shade trees and structures and to revise building methods and materials to reduce the daytime absorption and nighttime release of heat.

“These overnight temperatures are really the clearest consequence of our urban design, past to present,” Hondula said.

Nationwide, nighttime lows in the June-August summer season have risen an average of 2.6 degrees Fahrenheit since 1970, according to government data compiled by Climate Central. The increase is much higher in many cities of the West, and Phoenix’s nighttime average climbed 5.8 degrees in that time.

'There's a clear climate change signal here'

While concrete and blacktop play their roles, it’s not just fast-growing cities that are heating up. Detroit experienced similar heating, while Northeastern cities like Buffalo and Rochester, New York, warmed at rates closer to the national average.

“Of course we expect hot summers (in Arizona), but part of what we see with climate change is longer and more intense heat waves,” said Kathy Jacobs, who directs the University of Arizona’s Center for Climate Adaptation Science and Solutions. Still, the current heat wave’s intensity and duration is “not what we would expect in the absence of climate change.

“There’s a clear climate change signal here," Jacobs said, "but you can’t say which proportion is directly attributable to climate change.”

Jacobs has participated as an author or reviewing scientist in several iterations of the National Climate Assessment and led the Obama administration’s completion of the third assessment report.

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Most people who succumb to heat waves die from cardiovascular collapse, said Jennifer Vanos, an extreme heat researcher and associate professor in Arizona State University’s Global Futures Laboratory. The body seeks to cool itself partly by pumping hot blood toward the skin, she said, which can exacerbate heart conditions if it goes on too long. That’s one reason hot nights keep the danger elevated.

“The longer (the heart) has to do that without recovery, the more stressful it’s going to be,” Vanos said.

People often think that heat stroke, with core body temperatures above 108, pose the greatest danger, but core temperatures just over 100 can be dangerous for those with heart conditions. Victims may also suffer from kidney problems if they become dehydrated, she said, and may lose the ability to cool themselves by sweating.

Days on end without cooling also build the risk. “After a three-day heat wave, we see the highest numbers of deaths,” Vanos said.

For those who can’t stay cool at home, Vanos said, finding a cool place — even a shady area in a grassy park — can be critical to reducing heat stress. While some cooling stations close during the hot part of the day, she said, spending time in them can still provide a critical break.

People’s reactions to heat vary, she said, so it’s not clear how long it might take a given person to get their core temperature back to a safe level. She and colleagues are seeking to clarify that for people of various body types and with various conditions, using a high-tech manikin that senses both atmospheric and body-generated heat. But they just used it outdoors for the first time this week, and don’t yet have results to report.

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People with homes that lack functioning air conditioners may find some relief by setting a fan in front of buckets of water or soaked sheets, she said, so it will encourage the cooling effects of evaporation. That’s less effective on more humid days, when a fan alone would still help.

The Phoenix Neighborhood Services Department has programs to assist low-income residents with home weatherization and air conditioner repairs. The city’s Human Services Department assists low-income residents with utility bills through an online application or by phone at 602-534-AIDE (2433). The Arizona Department of Economic Security also assists with utility bills through the Low Income Home Energy Assistance Program, online or at 866-494-1981.

Information about cooling stations is available online at https://hrn.azmag.gov/.

Brandon Loomis covers environmental and climate issues for The Arizona Republic and azcentral.com. Reach him at brandon.loomis@arizonarepublic.com or follow him on Twitter @brandonloomis.

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This article originally appeared on Arizona Republic: Arizona's string of hot days risks repeat of 2022's record deaths