A recent study by the Illinois Institute of Technology and Elevate, a nonprofit organization focused on equitable climate solutions, reveals that Chicago families without central air conditioning face dangerous indoor temperatures during increasingly hotter summers. The research, conducted during a severe heatwave in 2023, showed that homes without central air conditioning experienced high temperatures even after outdoor conditions cooled overnight. Despite many participants feeling uncomfortably warm, only half recognized their homes as reaching unsafe temperatures.
The report, titled “Summer Indoor Thermal Conditions and Heat Adaptation in Chicago Residences,” includes contributions from Chicago’s Department of Environment (DOE) and the Chicago Department of Public Health (CDPH). It was funded by Northwestern University’s Buffett Institute for Global Affairs through the Defusing Disasters Working Group, which is developing Chicago’s first public health-informed Heat Vulnerability Index.
“This collaborative study is among the first to quantify the indoor temperature extremes using actual data measurements. Until now, we have had limited information on indoor temperature extremes during heatwaves, as most of our understanding was based on model results or focused mostly on outdoor measurements. Our study shows that each space within a home can respond differently to a heatwave, highlighting the need to provide a safe cooling space in every home,” said Mohammad Heidarinejad, associate professor of architectural engineering at Illinois Tech.
The findings indicate many families are unknowingly exposed to extreme heat, identified by the National Oceanic and Atmospheric Administration (NOAA) as the leading cause of weather-related deaths in the United States. Extreme heat can also cause heat stroke and exacerbate existing health conditions.
“The findings in this report were very powerful and confirm what is anecdotally expressed by many residents throughout the summer,” said Elevate CEO Anne Evens. “If homes are retaining extreme heat overnight, it’s dangerous. Simply put, Chicago residents need greater access to affordable cooling in their homes to stay safe during increasingly frequent and intense heatwaves.”
“Social isolation is one of the biggest risk factors in heat-related deaths,” said CDPH Commissioner Dr. Olusimbo “Simbo” Ige. “We know heat impacts neighborhoods and individuals differently; what we want to learn now is who exactly is being impacted so we can protect them.”
The report stresses the importance of policies and programs to protect people when air conditioning or hydration is unaffordable or unattainable. Researchers collected data on indoor temperature and humidity from 10 Chicago homes over four weeks during summer 2023, including one of the city's hottest recorded heatwaves. All monitored homes reached NOAA's "Extreme Caution" threshold of 90 degrees Fahrenheit; eight met the "Danger" threshold of 103 degrees.
“Recent decades have seen outdoor summer nighttime temperatures increase at twice the rate of outdoor summer daytime temperatures," said Northwestern Professor Daniel Horton. "Warmer nights limit the body’s ability to recover from daytime temperature extremes which exacerbates health risks."
As climate patterns shift, average summer temperatures in Chicago are expected to rise higher and sooner in the season with more frequent extreme heatwaves projected. This research empowers community leaders to implement better-informed strategies for increasing city resilience against severe weather events.
Last year Elevate and Illinois Tech coordinated an indoor air temperature study with HeatWatch Chicago under NOAA’s Urban Heat Island Mapping Campaign. Community volunteers helped measure air temperature across all 77 Chicago community areas creating urban heat island maps visualizing neighborhood disparities.
Following this effort, the Defusing Disasters Working Group began collecting various data sets including climate data and death certificates from the last 30 years to develop a public health-based Heat Vulnerability Index (HVI). This HVI aims to guide policy development improving heat resiliency in communities while preventing hospitalizations and deaths among at-risk residents.
Accessing comprehensive data remains a challenge especially regarding who has or cannot afford air conditioning which could refine HVI prioritization during extreme heat events.