Dehydration The third way heat kills is by lack of water in the body, or dehydration. As people sweat, they lose liquids to a point that can severely hurt kidneys, Professor Jay said. He added that dehydration also reduces blood flow and worsens cardiac problems. Renee Salas is a Harvard University professor of public health and an emergency room doctor at Massachusetts General Hospital. "Dehydration can be very dangerous and even deadly for everyone if it gets bad enough, Salas said. But it is especially dangerous for those with medical conditions and on certain medications," she added. How heat affects the brain Heat also affects the brain. It can interfere with thinking and reasoning. Kris Ebi is a public health and climate professor at the University of Washington. She said one of the first signs that heat has become dangerous is mental confusion. However, the person suffering from the heat is unlikely to see it, she said. This becomes a bigger problem as people age.

Many people may not realize their danger, Houstons Gandhi said. Dehydration can progress into shock. This causes organs to shut down from a lack of blood, oxygen, and nutrients. One definition of heatstroke is having a core body temperature of 40 degrees Celsius combined with mental confusion and difficulty thinking said Pennsylvania State University physiology professor W. Larry Kenney.

Wet bulb and hot box test Some scientists use a complex measurement tool called wet bulb globe temperature. It records humidity, solar radiation, and wind. In the past, it was thought that a wet bulb reading of 35 Celsius (or 95 Fahrenheit) was the danger point. Kenney also runs a hot box laboratory and has done nearly 600 tests. He said his tests show the wet-bulb danger point is closer to 30.5 Celsius. And that temperature is for young healthy people. For older people, the danger point is a wet bulb temperature of 28 degrees Celsius, he said. He adds that the amount of moisture in the air, or humidity, plays a big part. "Humid heat waves kill a lot more people than dry heat waves," Kenney said. Heatstroke is an emergency. Medical workers try to cool a victim down within 30 minutes, Salas said. Shes the professor and emergency room doctor in Massachusetts.

The best treatment is a cold water bath. But Salas said that those baths are not always available. So, emergency rooms pump patients with cool fluids intravenously, apply cold water to the skin, put ice packs in armpits and groins, and place them on a cold mat with cold water running inside it. However, sometimes all these treatments do not work. Experts call it a silent killer: You do not see the damage happening. Much of the United States, Mexico, India, and the Middle East suffer through extreme heat waves. These heat events are worsened by human-caused climate change. Climate change made a killer heat wave in Mexico and the Southwest U.S. even warmer and also made it 35 times more likely to happen more often. Extreme heat in India has killed more than 100 people in the past three and a half months.