Cook County has recorded at least 14 heat-related deaths this summer, with July emerging as the deadliest month for heat-related fatalities in over a decade, according to data from the county medical examiner’s office. The region experienced multiple heat waves from late June through mid-July, during which the heat index—a measure combining temperature and humidity—rose above 100 degrees for several consecutive days.
Most of the individuals who died had preexisting health conditions such as cardiovascular disease, hypertension, and obesity, which were exacerbated by the extreme heat. Medical experts note that intense heat places additional stress on these underlying ailments, potentially triggering heart attacks, strokes, and heart failure. However, identifying deaths directly attributable to heat remains challenging because coexisting health issues can obscure the role of elevated temperatures.
Abel Kho, an internist and professor of medicine and preventive medicine at Northwestern University’s Feinberg School of Medicine, highlighted the likelihood of undercounting heat-related deaths, pointing to limitations in the documentation process on death records. He noted that these challenges in accurately recording heat as a factor in mortality have long been recognized.
Researchers emphasize the need for clearer scientific and clinical links between heat exposure and health outcomes to improve public health responses amid the growing risk of prolonged and intensified heat waves due to climate change. Daniel Horton, a Northwestern associate professor and leader of the Defusing Disasters Working Group at the Buffett Institute for Global Affairs, stated that heat causes multiple negative health effects that precede mortality and should be better understood.
Supporting this view, a recent Northwestern study published in Science Advances identified 33 medical conditions linked to extreme heat during the past 13 years in the Chicago area. These ranged from skin rashes and leg swelling to kidney disease, multiple sclerosis, and certain mental health disorders, expanding the scope of heat-related health issues beyond the commonly recognized dehydration and heat stroke.
The impact of extreme heat disproportionately affects communities of color in Cook County, where rates of chronic respiratory and cardiovascular diseases exceed city averages. More than half of the heat-related deaths reported this summer were among people of color, including five Black individuals and four Latino individuals.
Eleven of these fatalities occurred within Chicago city limits, notably in South and West Side neighborhoods such as East Garfield Park, Near West Side, Englewood, and Chatham. Most of these deaths happened close to green spaces or designated cooling sites like libraries, police stations, senior centers, or park district facilities. This proximity has raised concerns that public awareness and accessibility of cooling resources remain insufficient, especially during nights, weekends, or holidays, affecting vulnerable populations such as the homeless or those lacking air conditioning at home.
Ponni Arunkumar, the Cook County chief medical examiner, explained that not all suspected heat-related deaths fall under the office’s jurisdiction, as treating physicians often certify deaths without involving the medical examiner when heat is considered a factor. This practice contributes to underreporting. She also noted that determining heat as a cause can be delayed due to necessary toxicology testing and the challenge of diagnosing heat stress or hyperthermia by exclusion, particularly when body temperature at death is unknown.
The presence of stimulant drugs like cocaine or amphetamines can increase a person’s susceptibility to heat-related health issues by raising body temperature. Additionally, health complications and fatalities linked to heat exposure can occur days or even weeks after a heat wave ends, complicating efforts to attribute cause accurately.
Experts advocate for enhanced medical record-keeping and integration of broader clinical data to strengthen the association between heat exposure and health outcomes. Such improvements would be crucial for refining public health strategies as climate change continues to raise the frequency and severity of extreme heat events.