A New Investigation About Who’s Getting Sick From Heat-Related Illness Should Be a Wakeup Call for America

“Zip codes do determine your health, and most of that is because of structural racism.”

Joanna Eberts for the Center for Public Integrity

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This story was produced in collaboration with the Center for Public Integrity and Columbia Journalism Investigations. It was co-published in partnership with Mother Jones, The Arizona Republic, and Orlando Sentinel. Regional stories based on the heat illness data analysis produced by CJI can be found in Orlando Sentinel and The Arizona Republic.

Mario Wilcox won’t set out in the summer without an emergency kit in his car trunk: a cooler with an ice pack and a blanket. He learned this improvised life saver from his time in the Iraq and Afghanistan wars; ice and a wet cloth can cool down an overheated body. Now he finds it vital in the intensifying heat of Fort Pierce, Florida, and especially his heat-stressed neighborhood.

More than 2,000 miles away in Phoenix, Arizona, Grace Salinas monitors the street outside her window in a public housing complex when summer temperatures reach triple digits. A community leader in the area southwest of downtown, Salinas stocks cold water bottles for anyone she sees struggling with the heat, a situation growing more common each year. 

Sgt. Mario Victorez Wilcox takes a break after volunteering at a community food giveaway, Friday, Nov. 20, 2020, in Fort Pierce, Fla.

Phelan M. Ebenhack

Heat-related illnesses are soaring in Arizona and Florida as the planet warms and temperatures rise. Among the hottest states in the country, none saw a sharper spike in summertime temperatures over the last century than these two. Already, Arizona is considered the hottest state in the US, and Phoenix the hottest city, with more than 140 days over 100 degrees Fahrenheit last year alone. In Florida, the combination of heat and humidity makes it one of the nation’s most dangerous places, according to a recent study.

Poor communities are bearing the brunt of sickening heat in these states, an analysis by Columbia Journalism Investigations and the Center for Public Integrity found. Federal data capturing most emergency room visits and hospitalizations in Arizona and Florida reveal higher rates of heat-related illnesses in areas with less income. The data, never before made public at the zip code level, also show that the highest rates of heat-related illnesses are in neighborhoods with a history of racial segregation. Experts say racist policies of the past created conditions, never corrected, that make heat more dangerous for people there today.

Winter has arrived in Arizona and Florida, attracting northerners eager to escape the cold. It seems easy to forget scorching temperatures now. But the warming planet will continue to make summers hotter and more deadly. And that means the problem requires attention year round.

“You would never decide not to heat your home because it is only useful in the winter,” said Howard Frumkin of the University of Washington School of Public Health, who headed the U.S. Centers for Disease Control and Prevention’s climate program in the mid-2000s. Likewise, the best solutions for extreme heat—planting more trees, creating buddy systems—must be implemented consistently to be effective. If “efforts lag for months at a time,” he said, “then you lose ground.”

The response to the problem in these hotspots is as disparate as the landscape itself. In the desert city of Phoenix, grassroots groups are partnering with government officials to protect low-income Black and Latino residents from the scorching sun, but targeted and long-term solutions have yet to come. In the beachfront city of Fort Pierce, by contrast, local authorities barely recognize the threat of heat and are doing little to nothing about it. 

Adrienne Hollis, a researcher at the Union of Concerned Scientists, studies the effects of the changing climate on the health of historically disadvantaged populations. She notes that communities of color are often the hardest hit by extreme heat. According to her calculations, US counties where African Americans or Latinos represent at least a quarter of the population—most in the South—have faced more days with temperatures above 100 degrees Fahrenheit over a three-decade period: an average of 18 and 13 days per year, respectively, as compared with roughly seven days a year for the rest of the country. 

“Zip codes do determine your health,” Hollis said, “and most of that is because of structural racism.” 


 Arizona’s 85007 zip code, which includes both the predominantly low-income Black and Latino area southwest of downtown and the more affluent, white neighborhood of Encanto Park, had in 2017 the highest rate of heat-related illness in that state. CJI’s analysis of the federal data shows per-capita ER visits and hospitalizations linked to problems such as heat stroke, heat exhaustion and dehydration in this 4.5-square-mile area were nearly 10 times the state’s average. In Florida’s 34950 zip code, the majority Black and low-income neighborhood of Lincoln Park where Wilcox lives, residents came to hospitals for these ailments nearly six times more often than the statewide average.

The situation in both places has been getting worse, county health data shows. In and around southwest of downtown Phoenix, the yearly number of heat-related ER visits for every 100,000 people has more than doubled since 2010, to 129. In Saint Lucie County, where Lincoln Park is located, the rate of such visits in recent years is almost double its mid-2000s level, while hospitalization rates in the same period have more than tripled. 

A home southwest of downtown Phoenix, where fewer trees, shadeless bus stops and a lack of financial resources makes heat more dangerous.

Nick Oza / The Arizona Republic

Emergency calls to 911 in both places reveal the risks faced by residents during the summer and even well into the fall. Elderly people, overcome by heat, collapsed and injured themselves while walking outside. Heat exhaustion hit young adults as they biked or waited for a bus. Potentially deadly heat strokes snuck up on workers laboring in the sun.

Salinas, 70, who grew up in Phoenix’s 85007 zip code, is used to seeing people succumb to the baking sun. She lost a cousin who lived in the neighborhood to heat stroke and witnessed her adult son, sprawled on the ground outside her home, go to the ER for the same reason. She knows how to identify the danger signs. “We see people walking by looking like they need to breathe,” she said. “If you’re not sweating anymore, you’re already in trouble.” During the summer, the tenant leader also checks on elderly people living in her public-housing complex, built in the 1940s to house Mexican Americans. She gives people tips on using the air conditioner in more economical ways. 

That may sound like a constant battle. And it is. 

“It’s just the way of life here,” Salinas said.

Unequal Heat

What’s driving this problem is inequality. Salinas lives in an area largely populated by squat houses with dusty yards that rivals the hottest spots in Phoenix. Daytime temperatures here can be between four and seven degrees Fahrenheit higher than in the wealthier Encanto, located partly in the 85007 zip code just three miles north, according to separate experiments conducted by Arizona State University and the Arizona Republic

While Encanto is an oasis full of parks, replete with trees that keep the air cooler, the area southwest of downtown, between West Harrison Street and the Maricopa Freeway, is marked by barren lots and heat-trapping cement. Mirage-like desert mountains on the horizon break up the urban landscape of highways, buildings and fences here. To make things worse, this area is one of the poorest in town, with residents who often can’t afford to run an air conditioner. Electricity bills can cost around $600 a month per family.

It’s a dangerous combination.

“That’s where the inequities show,” said Juan Barreto-Declet, a geographer researching environmental vulnerability to heat in Phoenix. “That is where the vulnerability is higher.”

And those inequities appear to be widening. State health data shows heat illnesses in this neighborhood and across central Phoenix have increased at a rate seven times the rest of the city since 2010. In Encanto, by contrast, the annual rate of heat illnesses has dipped. 


CJI’s analysis shows 79 people who live in the 85007 zip code went to the hospital in 2017 because of life-threatening symptoms brought on by heat. Around half suffered from heat exhaustion, while another 20 percent succumbed to the more severe condition of heat stroke.

The risks facing residents in this area didn’t happen by chance. Investments here—in trees, parks, transit—have been historically lower than in higher-income areas of the city. 

That history dates back at least as far as government-imposed “redlining” of the 1930s. The federal Home Owners’ Loan Corp. mapped neighborhoods in cities across the country and graded them according to perceived risk of lending there—with race as the key factor. Areas with people of color and immigrants were marked in red and judged high-risk for mortgage lenders, starving neighborhoods of investment. 

The government’s red pen came for the south and west sides of Phoenix, among the city’s oldest regions and historically inhabited by Blacks, Mexican immigrants and Native Americans. Local decisions reinforced residential segregation: Zoning regulations forbade industrial land use in white neighborhoods, funneling that development and its pollution to places where people of color lived; race-restrictive covenants prevented anyone who wasn’t white from buying houses in affluent suburbs. 

These policies resulted in “relegating minorities and low-income populations to the hottest areas of the city,” Barreto-Declet said.

A similar storyline has unfolded in many other places across the country — including Florida’s heat-illnesses hotspot, Lincoln Park in Fort Pierce. 

The area’s first Black people were enslaved, brought by white settlers on the hunt for land along the Atlantic Coast in 1842. More African Americans moved to the region after the Civil War to work on pineapple farms and then railroads. 

The Jim Crow era hardened this segregation. Lincoln Park residents couldn’t go to the same school or beach as white people. Celebrated writer Zora Neale Hurston, who spent her last years in the neighborhood, was buried in an all-Black cemetery, her grave unmarked for a dozen years. The now-shuttered African American-owned theater — one of just four in the country — stands on the main thoroughfare here, Avenue D. U.S. 1 was the literal dividing line: the “Colored Town” on one side, and on the other, the “White City.” 

“Segregation in the county determined where a Black citizen could live, work, go to school, fish, eat, give birth, go to church, pee, walk and be buried,” said Jean Ellen Wilson, an 80-year-old historian who grew up in the white part of town. “Black people were not allowed to come out to White City.”

Block homes are viewed in the Lincoln Park neighborhood, Friday, Nov. 20, 2020, in Fort Pierce, Fla.

Phelan M. Ebenhack

Today, most of the city’s Black residents still live in Lincoln Park, which remains “Fort Pierce’s most segregated community,” a 2016 city housing report states. The neighborhood is 91 percent African American, and a little more than half the residents live below the federal poverty line. In a county where the typical household makes about $43,000, the median income here is just $15,797. One aid agency fields 300 or so monthly requests from local residents seeking help to pay their electricity bills.


Wilcox sees the stark difference between his neighborhood and the rest of the city when driving in the area. Heading south on Indian River Drive, toward the Fort Pierce immortalized in paintings of exuberant sunrises and palm-lined beaches, he takes in solar panels, fountains, expensive houses. On the return trip north, he spots weathered homes and stores, their pastel colors faded, their windows boarded or covered in aluminum foil — a sign of no air conditioning or insulation. On a hot day, families keep doors open and sit outside to cool off. Friends play dominoes or catch ball on street corners. As he sees it, a systematic lack of resources explains why people here are sickened by heat. 

“The south and the beachfront are the haves,” he said. “And the north of the city is the haves not.” 

CJI’s data analysis shows that 33 people living in the zip code encompassing most of Lincoln Park went to the hospital for heat-related illnesses in 2017. Sixty percent were Black. That’s a lot of people for a small area of about 16,000 residents. 

The legacy of racist policies on present-day heat vulnerability is widespread across the country. A study conducted by researchers at the Science Museum of Virginia, Virginia Commonwealth University and Portland State University looked at more than 108 cities to conclude that the hottest neighborhoods are those located in formerly redlined areas. Unpublished data from this research, calculated exclusively for CJI, shows that in Phoenix, for example, the current difference in temperature between redlined areas and other neighborhoods is more than eight degrees Fahrenheit during the summer.


In the city’s 85007 zip code, home to several shelters, people identified as homeless account for some of the patients sickened by heat. But even when this population is excluded from the data, the zip code remains the state’s hardest hit. And Black people are disproportionately represented among the heat-illness patients, CJI’s analysis shows: They’re three times more likely to go to the ER for that reason. 

CJI analyzed statewide data in Arizona and Florida to see whether the zip codes with the highest heat-illness rates were also the hottest, but the results were inconclusive. Heat maps show Fort Pierce’s Lincoln Park and neighborhoods southwest of downtown Phoenix have elevated temperatures, but other similarly hot areas have experienced fewer heat illnesses. That suggests temperature isn’t the only reason so many people are sickened by heat in these neighborhoods.

Underlying health conditions that exacerbate heat illness may play a role. In both zips, CJI’s analysis of hospital data found high numbers of patients diagnosed with conditions known to heighten risk for heat stress — diabetes, hypertension, heart disease. In Lincoln Park, nearly half of the 2017 heat-illness patients were also diagnosed with diabetes or hypertension. This too can be a consequence of decades of decisions that sapped neighborhood resources. 

One 2017 community assessment found the diabetes rate is three times higher in Lincoln Park than in the rest of the county, a spike that its health department has worked to reduce. Most health experts recognize the link between poverty, chronic conditions and heat, but it doesn’t seem to be on county health officials’ radar.

Clint Sperber, who heads the Saint Lucie County Department of Health, declined to be interviewed for this article. In an email, he acknowledged that the agency wasn’t aware of the heat issue until a CJI reporter reached out. The agency had no answer about why it had not already made use of the data on heat illnesses that the Florida Department of Health collects so its county counterparts can develop public health interventions.  

“The Department of Health in St. Lucie and our community partners have been informed, and as a community we will collaborate to address this issue,” Sperber wrote in a November 12 email.

The agency has taken the problem to the Fort Pierce city manager, he said. A spokesperson for that official, Nick Mimms, said in an email that the city is “looking forward…to collect as much data and information as possible in order to combat the heat illness and create a program that provides safety and protects the well-being of its citizens.” Mimms declined an interview request.

Gerald Newberry, 59, was born and raised in Lincoln Park and has always worked outdoors, starting as a teenager when he picked fruit with his father. He lost count of how many times he saw co-workers getting sick in the fields because of the baking sun. On the job, farmworkers with limited access to health care relied on a homemade treatment to beat the heat: a teaspoon of apple cider vinegar mixed with water. Now a landscaper, Newberry still carries a vinegar and water bottle with him. Often, he gets dizzy and feels ill under the sun. 

“It feels like you did bump your head, it feels sore, and you know that you didn’t bump it,” he said. “And then another thing is the headaches, heavy headaches.” 

He has never fainted but fears the day he will, like the locals say, be “bear-caught,” a heat stroke that takes you to the ground like a bear sneaking in from behind. Until he recently got health insurance, sporadic visits to Walgreens to check his blood pressure were his only form of health care. 

Too Slow or Not at All

Cities can mitigate heat risk with steps such as planting trees, investing in new designs and cool materials, and opening cooling centers for residents without air conditioning. None of this has happened in Fort Pierce, the health department said. In one of the city’s few nods to the dangers, it prohibits residents from leaving dogs outside when the heat index is above 100°F. There’s no local law protecting people from heat.

A 2016 report from the county emergency-management division at the Department of Public Safety warned that the “probability of heat indexes within the range of causing health problems is moderate to high during the summer months.” But according to the division, the county has never declared a heat emergency and, unlike hurricanes and floods, the issue is not among its priorities. 

County health officials also confirm that they don’t have any programs or policies for extreme heat. In a 2015 report, the Florida health department classified Fort Pierce’s county, Saint Lucie, at medium to high risk for heat hazards under different climate change scenarios. But the state’s actions to prevent heat illnesses are scant. Its “Beat the Heat” campaign is a 26-second video with tips for residents about how to stay safe.

State health officials have long overlooked climate-related health hazards. In 2016, the department shunted its federally funded climate and health program to Florida State University, where it has no policy-making power. The program serves three of the state’s 67 counties. Saint Lucie isn’t one of them.

Former Fort Pierce City Commissioner Reginald Sessions, a native of Lincoln Park who represented the area until December, said he’d like to see more effort by health officials to help Black and poor communities. 

“We need to put a lot more emphasis on targeting them to improve their health,” he said. “I assure you that if we do that, we will have less African Americans suffering from heat strokes.”

In Phoenix, where local officials are keenly aware of heat’s dangers, efforts to protect residents are further along. But plans to address the long underinvestment in neighborhoods southwest of downtown have yet to bear fruit.  

Efforts to save lives with heat-risk awareness campaigns date back to the summer of 2009, after eight local residents died of heat stroke. 

Eva Olivas with the grassroots Phoenix Revitalization Corp. reached out to the city parks and aquatics departments. They organized information sessions at public pools and posted on social media. 

“Sometimes people who live here get so used to the heat that they forget how dangerous it can be,” she said. “The idea was to remind them that the summers today are not like summers before.”

Mark Hartman, who heads the city’s Sustainability Office, said Phoenix is trying to be the first municipality to respond to extreme heat like other places prepare for storms. In 2018, he and other city officials launched a “Heat Ready” program that pulled together actions they had already adopted and plan to extend, including emergency relief such as cooling centers and long-term initiatives, like planting trees and using “cooling pavement” that doesn’t absorb as much heat. His office is testing this pavement in different districts across the city, including one location outside the 85007 zip code in the area southwest of downtown.

Phoenix has set a goal to cover 25 percent of its land area with trees by 2030. That would double the tree canopy and require planting 10,000 trees per year on average. But the city is off track: When Phoenix planted a record number of trees in 2019, it still amounted to less than half the annual requirement. 

A CJI analysis of satellite data reveals a stark disparity in green space in zip code 85007: Forty-two percent of the wealthier Encanto neighborhood has leafy vegetation, including two golf courses. By contrast, just seven percent of the area southwest of downtown Phoenix is green. Residents have pushed city officials for years to plant more trees in vulnerable areas, and a city subcommittee recommended the appointment of a “tree administrator.” 

City officials have yet to implement that recommendation. Hartman said the city is trying to map the areas most in danger from heat to target tree distribution and related actions. 

“We originally thought that we needed to create shades throughout our whole city and trees everywhere, but actually, we just need them in certain places, like in vulnerable communities,” he said. 

In the last three years, his cabinet has worked with researchers like David Hondula, a sustainability scientist at ASU and a member of the state’s climate and health team, to develop a more complete vulnerability index. It aims to take into account not only where the most heat-vulnerable people live, but also where they are most exposed. 

“The traditional approaches to vulnerability don’t really reflect how people move around the city,” said Hondula, whose own research has identified zip code 85007 among the city’s top 10 neighborhoods most vulnerable to heat. 

Advocates, scientists and county health officials have met multiple times with residents of Edison-Eastlake, a neighborhood just east of downtown Phoenix, to hear about problems contributing to heat risk. Among those they named: too few street trees and unshaded bus stops. 

This shouldn’t come as news to city officials. A 2004 Phoenix urban design plan recommended the city “provide comfortable and convenient shaded bus stops.” But from her office window today, 16 years later, Olivas sees a bus stop that’s merely a sign in the sun. “Should this kind of ‘infrastructure’ be considered normal in a city where the temperatures get up to 117?” she asks.

That’s just one such example of a missed opportunity. In 2014, the city launched a streets plan that included guidelines for developers on shade and tree coverage. Four years later, seven of the project’s nine advisory board members quit, saying the city, lobbied by developers, was proposing a series of alterations to the street design guidelines that “watered them down” until they were meaningless. The project stalled.

“The city is really good at writing press releases and approving plans,” said Stacey Champion, who participated in a 2018 petition to Phoenix officials about local trees, “but not so good in making sure those plans actually get followed.”

Hartman, acknowledging some problems, blamed a lack of funding and personnel. He said the city still “has a long way” to go to be heat ready. 

Mayor Kate Gallego, asked about criticism that the city has prioritized plans over action, declined to comment. Her office pointed to yet another plan: a climate-action strategy it’s developing after joining a network of 96 municipalities worldwide whose leaders have committed to combat global warming. It will include heat mitigation.

“Phoenix is uniquely experienced to share proven practices for building heat resilience,” Gallego said​ in a written statement. “We are still learning and have a lot of work to do, but our partnership with heat research powerhouse Arizona State University and our legacy of living with heat makes Phoenix a model for other cities who are grappling with this public health challenge.”

A Hotter Future

If officials don’t counteract the longstanding disinvestment that endangers people in communities like Lincoln Park and those southwest of downtown Phoenix, heat risks there will worsen. A report from the Union of Concerned Scientists predicts Florida will experience some of the most frequent periods of extreme heat in the nation by 2050 as climate change intensifies: as many as 105 days a year with a heat index over 100°F. The group expects Fort Pierce and the surrounding county will endure five times more extreme heat days a year than from the 1970s to 2000. In the greater Phoenix area, such days are projected to double.

The UCS’s Hollis, who grew up in hot and segregated Mobile, Alabama, warns that people of color will bear the brunt of this change. By midcentury, if nothing is done to stop climate change, counties where Black residents make up more than a quarter of the population will experience an additional month of extreme heat days each year compared with their counterparts, according to an analysis she conducted.      

“If nothing is done,” she said, “we’re gonna have more health disparities, more people sick and more deaths.”

Back in Phoenix, Grace Salinas has tried to keep up her usual heat outreach. Amid the coronavirus pandemic, her block watch association had to abandon its plans for awareness campaigns and other activities. She sent information leaflets to neighbors instead. 

The number of 911 heat-related calls in the city last year topped 1,400. In the last six years, those calls have jumped 80 percent.

Sofia Moutinho and Elisabeth Gawthrop are reporting fellows for Columbia Journalism Investigations, an investigative reporting unit at the Columbia Journalism School. Funding for CJI comes from the school’s Investigative Reporting Resource and the Energy Foundation. The Center for Public Integrity provided editing, fact-checking and other support. The Arizona Republic provided photography.


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Learn more in “Less Dreading, More Doing,” where we lay out this wild moment and how we can keep charging hard for you. And please help if you can: $5, $50, or $500—every gift from every person truly matters right now.

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