Hot weather in summer can be dangerous for people who do sports or exercise outside. Experts from UCLA say that when the temperature is over 90°F (32°C), the body may not stay safe, especially if the air is humid. The National Oceanic and Atmospheric Administration says that a heat index of 90 to 103°F is a warning sign. Over 103°F is very dangerous. The body tries to stay at 98.6°F (37°C) by making sweat. But if there is too much moisture in the air, sweat cannot dry fast. This makes it hard for the body to stay cool. It can cause problems like dehydration, heat exhaustion, or heat stroke.

The Centers for Disease Control and Prevention says that heat can hurt the heart, lungs, and muscles. People may feel weak, dizzy, or sick to the stomach. These problems can get worse if people do not stop and rest. Experts say it is best to exercise early or late in the day, take breaks, stay in the shade, and drink plenty of water. Some people do not notice how hot they really feel. It is important to be careful and follow safety steps in very hot weather.