At Least 14 People Died From Heat in Cook County This Summer. Experts Say the Real Number Is Much Higher.

At least 14 people died from heat-related causes in Cook County, Illinois, this summer. July was the deadliest month for heat deaths in the county in more than ten years. Two heat waves hit the area in late June and mid-July, pushing the heat index — a mix of temperature and humidity — above 100 degrees for several days. Health experts say the true number of heat deaths is likely far greater than official records show.

Most of the people who died had health problems that were made worse by the extreme heat. These included heart disease, high blood pressure, and obesity. Extreme heat puts extra stress on the body, which can trigger heart attacks, strokes, and organ failure. When someone already has a serious illness, it can be hard to tell whether heat — or the illness — was the main cause of death.

That is why experts believe heat deaths are being undercounted. Dr. Abel Kho, a professor at Northwestern University, said the problem comes down to how deaths are recorded. Howard Ehrman, a former Chicago health official, thinks the real number could be 20 to 40 times higher than the official count. 'It's probably 20, 30, 40 times that,' he said.

Chicago knows the danger of deadly heat well. A heat wave in 1995 killed more than 700 people in the city. In recent years, heat deaths had been much lower — as few as three per year from 2020 to 2024. But this summer's death toll has shocked many health professionals and raised new concerns.

Experts say heat kills more people than any other extreme weather event. Human activities, like burning fossil fuels, release gases that trap heat in the atmosphere. This has caused Chicago's average summer temperatures to rise by nearly 2 degrees since 1970. Summer nights have also gotten warmer, giving the human body little time to cool down and recover.

The Cook County chief medical examiner, Dr. Ponni Arunkumar, explained that her office does not get called to investigate every suspected heat death. Sometimes a patient's doctor signs the death certificate without noting heat as a cause. 'There is that underreporting,' she said, as some cases slip through the cracks. This means some heat deaths never make it into the official count.

A new study from Northwestern University found that heat is linked to many more health problems than most people realize. Researchers looked at emergency room visits in the Chicago area over 13 years. They found 33 different health problems connected to heat, including skin rashes, kidney disease, mental health disorders, and even increased traffic accidents. Study author Daniel Horton said this is because heat causes stress on both the body and the mind.

Heat hits some communities harder than others. In Chicago, neighborhoods on the South and West Sides had the most heat deaths this summer. More than half of the people who died were people of color. Experts say this is partly because those communities have higher rates of chronic illness and fewer resources to stay cool, like air conditioning.

Cooling centers — like libraries, police stations, and park fieldhouses — exist to help people escape the heat. But many people who died this summer lived just blocks from one of these centers. Advocates say the city does not do enough to let people know about these resources, and many centers are closed overnight and on weekends. This makes it very hard for homeless people or those without air conditioning to get help when they need it most.

Researchers say improving medical records could help save lives in the future. Better data would make it easier to see the connection between heat and illness, even when heat is not listed as the main cause of death. 'I think there's a real opportunity for us to try to tie together different types of data,' Dr. Kho said. Understanding the full impact of heat on human health is a key step toward protecting communities as summers grow hotter.