Heat is the deadliest weather phenomenon, killing more people in an average year than hurricanes, tornadoes, floods and cold, according to the National Weather Service. Heat kills some outright via heat stress. For others, heat exacerbates common chronic conditions, including asthma, heart disease and diabetes.
In 1995, an estimated 740 Chicagoans infamously died as a result of a four-day heat wave — more than 400 in the initial tally and hundreds more from conditions aggravated by heat, as determined by a Chicago Public Health Department epidemiologist. People without air conditioning made up the majority of deaths deemed avoidable by federal health authorities.
“We will see more heat waves like the ‘95 Chicago heat wave,” said Elena Grossman, director of the Building Resilience Against Climate Effects program at the University of Illinois at Chicago. “That will become a constant reality.”
As climate change increases the frequency and intensity of heat waves, city dwellers face extra risk thanks to the urban heat island effect, in which man-made changes to the environment drive up temperatures in metropolitan areas.
Temperatures also vary within city borders, putting vulnerable populations in even more danger. To intervene where aid is most needed, local officials and organizations in dozens of cities have participated in a National Oceanic and Atmospheric Administration program launched in 2017 to map heat disparities and raise public awareness.
But Chicago has never applied, according to NOAA. So the Tribune set out to identify which communities may be more at risk and assess whether the city’s government is doing all it can to help them survive before the next heat wave strikes.
To provide Chicagoans access to temperature trends in their communities, the Tribune partnered with researchers at Boston University’s Center for Climate and Health to create a searchable map showing average summer surface temperatures across the city.
City agencies promote the use of six official cooling centers and an array of other air-conditioned public locations, such as libraries, during heat advisories. But the Tribune’s Boston University research partners found that substantial swaths of the city’s most vulnerable communities, with the hottest average surface temperatures, have no access to public cooling within walking distance of a half-mile.
In setting out to identify Chicago’s hottest areas, the Tribune realized that data from regular temperature sensors on the ground — such as those at O’Hare and Midway airports — couldn’t paint a complete picture. Temperatures can vary from community to community — sometimes from block to block. The answer: Data from passing satellites.