The Korey Stringer Institute at the University of Connecticut was named after an N.F.L. player who died of exertional heatstroke. The lab’s main research subjects have been athletes, members of the military, and laborers. But, with climate change, even mild exertion under extreme heat will affect more and more of us; in many parts of the United States, a heat wave and power outage could cause a substantial number of fatalities. Dhruv Khullar, a New Yorker contributor and practicing physician, visited the Stringer Institute to undergo a heat test—walking uphill for ninety minutes in a hundred-and-four-degree temperature—to better understand what’s happening. “I just feel puffy everywhere,” Khullar sighed. “You’d have to cut my finger off just to get my wedding ring off.” By the end of the test, Khullar spoke of cramps, dizziness, and a headache. He discussed the dangers of heatstroke with Douglas Casa, the lab’s head (who himself nearly died of it as a young athlete). “Climate change has taken this into the everyday world for the everyday American citizen. You don’t have to be a laborer working for twelve hours, you don’t have to be a soldier in training,” Casa tells him. “This is making it affect so many people even just during daily living.” Although the treatment for heat-related illness is straightforward, Casa says that implementation of simple measures remains challenging—and there is much we need to do to better prepare for the global rise in temperature.