A massive study shows what illnesses and injuries spike in emergency room visits during heat waves in Chicago. Researchers at Northwestern University examined more than 916,000 records from 2011 to 2023. They found that when the temperatures hits 92.6 degrees or above, hospitals see increases in more than a dozen injuries and illnesses, including unexpected issues like multiple sclerosis complications and marijuana-related mental health problems. Gunshot wounds and assault injuries soar. Experts say Wednesday's study highlights the health risks of heat and how climate change is putting a strain on the health care system. Doctors caution that when it's hot, people with chronic conditions need to be extra careful.