Mapping Out Extreme Heat Resilience Strategies for Cities
Defusing Disasters Global Working Group co-lead Daniel Horton and member Kyra Woods welcome community volunteers to their Heat Watch Chicago initiative’s activation day.
As summer temperatures reach new highs, the Defusing Disasters Global Working Group is measuring how extreme heat and heat vulnerability vary across Chicago.
Nearly 100 volunteers fanned out across Chicago to measure extreme heat on one of the hottest and clearest days of 2023. Volunteers drove around the city after fixing heat sensors to their car windows, capturing heat and humidity across its neighborhoods. Like a giant mobile thermometer, these sensors measure temperature and humidity on the ground, showing how the weather feels to people as they walk through their neighborhoods.
That summer day was known as Heat Watch Chicago activation day to members of the Buffett Institute’s Defusing Disasters Global Working Group. Members hail from a broad range of fields, from emergency medicine and disaster management to Earth sciences and environmental engineering. They represent municipal organizations that include the Chicago Department of Public Health, the Chicago Department of Environment and the Chicago Metropolitan Agency for Planning; academic institutions that include the University of Chicago, Rush University, the University of Illinois and the Chicago Area Patient-Centered Outcomes Research Network (CAPriCORN); and community organizations and NGOs such as Elevate, People for Community Recovery and the Southwest Collective.
“Climate change is making heat waves more intense and last longer, and they’re going to happen more frequently. The compounding effects of climate change and urban heat islands can have severe consequences for public health,” said Daniel Horton, co-lead of the Defusing Disasters Global Working Group and Associate Professor of Earth and Planetary Sciences at Northwestern University’s Weinberg College of Arts and Sciences. “If we know there are residents that experience higher temperatures than others, then that’s something the city can plan for by implementing policies to build resilience and adaptive capacities within those neighborhoods.”
When temperatures hit over 90 degrees in late July 2023, the group mobilized a troop of nearly 100 citizen scientists—local residents armed with small, hand-held heat sensors. These volunteers collected heat and humidity data across the city to identify what populations in Chicago are most vulnerable to extreme heat—data that will be used to develop a Heat Vulnerability Index for the city.
Heat Watch Chicago volunteers were interviewed by ABC7 Chicago on the initiative’s activation day.
Across the globe, extreme heat is now more deadly than earthquakes, floods, hurricanes, lightning and tornados combined. In spring 2024 alone, India’s Health Ministry reported that a heat wave caused over 40,000 suspected heat stroke cases and resulted in the deaths of more than 100 people. In Bamako, the capital of Mali, hospitals reported a similar death toll in just the first four days of April.
As temperatures climb higher, exposure can trigger dehydration, exhaustion and even stroke in a matter of hours. If a person survives an extreme heat event, they may experience permanent disability, but even less dire chronic exposure poses special risks to aging populations and those with preexisting conditions.
As climate change makes heat waves more intense and persistent, the public health community is interested in mitigating urban heat islands—pockets of cities where sprawling blacktop, sparse natural areas and high concentrations of buildings and freeways cause the built environment to warm more than other neighborhoods.
For many cities, these heat islands correspond with existing patterns of racial segregation and disinvestment, making majority-Black and -Latino neighborhoods more likely to experience hotter temperatures during heat waves. Temperatures in heat islands are five to ten degrees higher than other areas. Five degrees may not sound like much in the grand scheme of things, but it can mean life or death for the communities that call these heat islands home.
During Chicago's 1995 heat wave, deaths above average, or “excess deaths,” exceeded 700 mortalities in the span of a week. While some parts of the city made it through the crisis relatively unscathed, extreme heat laid siege to predominantly Black neighborhoods long neglected by the city. Many people died in their apartments, trapped by poor ventilation, lack of air conditioning, lack of financial resources to use air conditioning or fear of cracking open a window because of violent crime in their neighborhoods.
Chicago saw scorching weather in June 2024, breaking an all-time daily temperature record that stood for 137 years.
Last year’s Chicago heat watch campaign found neighborhoods on the city’s South Side were the hottest, with some areas averaging nearly 12 degrees hotter throughout the day than their cooler counterparts.
Researchers and public officials have since banded together through the Buffett Institute’s Defusing Disasters Global Working Group to examine and prevent adverse health effects associated with extreme weather events. The group began by collecting data from the public, partnering with organizations like Blacks in Green, Mi Villita Neighbors and the People’s Response Network to keep track of what places people thought got especially hot during the summer and what places were great for beating the heat.
The group has since established a governance board composed of academics, city leaders and community members to help guide an equitable decision-making process for the development of the city’s first Heat Vulnerability Index. Teresa Horton, Associate Professor of Research in Anthropology at Northwestern's Weinberg College of Arts and Sciences, leads community engagement efforts for the group and believes this participatory model has made the difference.
The Defusing Disasters Global Working Group’s partner organizations led tours in Chicago’s neighborhoods most vulnerable to extreme heat, highlighting community-led initiatives to address heat inequities, including a permaculture “food forest” in North Lawndale.
“We have to engage with communities and businesses. We have to engage with policymakers at any and every level to use the data that we have and translate the information we have as academics into policy to make this world a better place,” she said.
The group is also engaging the public more broadly. At the end of 2023, they hosted a public event highlighting the results from Heat Watch Chicago and how data from the campaign can inform city practices and policies.
“It could mean different things to different residents,” Daniel Horton said. “It could mean that cooling centers are opened in areas that don’t have them now. It could mean that air conditioning units are distributed to people who don’t have them. It could mean that utility companies allow residents to use more electricity on extremely hot days, even though they might not be able to pay for it at all.” To gather data in support of such initiatives, members of the group collaborated on a study published by Elevate to measure summer indoor air temperature ranges in homes without central air conditioning.
Climate change will likely lead to longer, more frequent and more severe heat waves in the summer, making local interventions that can predict and mitigate the risks of extreme heat exposure essential. To lessen the impacts of extreme weather events, public health officials, health systems and emergency management teams must know which communities are most vulnerable to extreme phenomena.
Raed Mansour is Director of Environmental Innovation at the Chicago Department of Public Health’s Bureau of Community Health. As a Defusing Disasters group member and the lead organizer of Heat Watch Chicago, his office will use the group’s heat vulnerability indices to shape Chicago’s public health policy and strategies.
“A lot of the cities that work on this heat watch campaign immediately use it to inform where to plant trees in urban heat islands and getting these nature-based solutions in the ground will help, but I think we can do more with this,” said Mansour. “I have to credit Northwestern and the community working together because we were taking their time, fuel and vehicle to do something that will help the greater good.”
Following the success of their Heat Watch initiative, the group seeks to expand their programmatic work to address extreme weather phenomena beyond extreme heat. They are currently conducting research on climate and cardiovascular health with bioinformatics experts at multiple Australian universities and supporting a study led by a researcher from the University of Hamburg in Germany comparing heat, air quality and health between Hamburg and Chicago. Ultimately, the group hopes to expand their collaborative approach outside of Chicago and the U.S. to help cities around the world build resilience to extreme weather phenomena.
“When it comes to climate change and extreme events, we know that disadvantaged communities suffer the brunt of these impacts in the U.S. and abroad,” said Daniel Horton. “Other cities across the world have developed Heat Vulnerability Indices, but very few have used a community-based participatory research model. That leaves a lot of people out of the development process, but it’s really important to have those voices in the room when you’re making decisions that will directly impact them. If other cities build on the model we’ve created in Chicago, community trust will be built in from the start.”