Heat-related illnesses occur when the body cannot properly regulate its temperature due to excessive heat exposure. Common types include heat exhaustion, characterized by heavy sweating, weakness, and dizziness, and heat stroke, a more severe condition that can lead to confusion, loss of consciousness, and even death. These illnesses are often caused by high temperatures, high humidity, and strenuous physical activity, especially in vulnerable populations like the elderly and young children. Prevention includes staying hydrated, wearing light clothing, and avoiding outdoor activities during peak heat hours. Recognizing symptoms early can help prevent serious health complications.