AINEWS
Heat is the deadliest weather. Here is what it does inside your body.
NPR's health team maps the three step cascade from sweat failing to heatstroke, and the small set of moves that interrupt it.
NPR's health team maps the three step cascade from sweat failing to heatstroke, and the small set of moves that interrupt it.
A kid on a summer soccer field stops running. A roofer sets down his tape. An older neighbor without air conditioning turns on a fan that just pushes hot air around the room. None of them look sick, but the clock inside their bodies has already started.
Heat is the deadliest kind of extreme weather, a characterization NPR's health team makes at the top of a comic published on June 13, 2026 that walks readers through how the body fails when temperature and humidity stack up. The piece, reported by Maria Godoy and drawn by Connie Hanzhang Jin, runs through three failure modes in sequence and pairs each one with a specific move the reader can make.
The body's main cooling system is sweat. Sweat cools because it evaporates, drawing heat off the skin as it turns to vapor. High humidity short-circuits the system: air that is already saturated with water cannot absorb more, so sweat sits on the skin and the body keeps gaining heat. The NPR explainer opens on this point, and it is the doorway to everything that follows.
The first failure mode is fluid and circulation. As the body pushes blood toward the skin to dump heat, blood pressure in the core drops. Sweating also pulls water and salt out of the body, and the longer that imbalance goes uncorrected, the harder the heart has to work to keep blood moving where it needs to go. The matching safety move is the obvious one: drink water before you feel thirsty, and keep drinking. NPR pairs the cascade with practical guidance: shade, cool water on the skin, and rest at the first sign of dizziness.
The second failure mode is cellular. Core body temperature climbs past the range the body's proteins are built to handle, and cells and organs take direct heat damage. This is also the stage where fans stop helping. A fan moves air across skin, but it only cools the body if that air is dry enough to accept more moisture. In humid conditions the fan just recirculates warm, wet air, and the body keeps heating up. The matching move, in the comic's safety hierarchy, is to wet the skin directly with cool water and get to an air-conditioned space or a designated cooling center.
The third failure mode is the one that turns a bad day into a medical emergency: heat exhaustion tipping into heatstroke. Heat exhaustion is the body's last organized protest, with heavy sweating, weakness, nausea, and a fast pulse. Heatstroke is the body losing the argument. Sweating stops, confusion sets in, and core temperature climbs past the threshold where organs recover on their own. Heatstroke is a 911 call, not a water break, and the NPR piece is explicit about the difference.
Read the failure modes alongside the people who face them first, and the safety list stops looking like a personal checklist. Outdoor workers, elderly people in apartments without air conditioning, and residents of low-income urban neighborhoods with little tree cover and few cooling centers are the ones the reporting flags as facing the longest clocks when a heat dome settles in. The hierarchy NPR lays out, water, shade, wet skin, low-humidity airflow, cooling centers, and a call for help if confusion sets in, lands differently once it is paired with that structural context. Individual advice works, and so does knowing which neighbor is most likely to need it this week.