 Cleveland Clinic psychologist Dr. Susan Albers says when the body has to work harder to keep cool, that causes the release of the stress hormone cortisol. During the heat waves, people tend to feel more agitated. Everyone's mood is impacted by the heat. Experts say prevention is key. That starts with drinking plenty of water. It's important to stay cool and to hydrate. Be sure to monitor for signs of heat exhaustion, such as heavy sweating, dizziness, fatigue, headache, and fast heartbeat.