Final answer:
The most serious heat-related medical condition resulting in the need for immediate medical attention is heat stroke. Symptoms include high body temperature, altered mental status, hot and dry skin, rapid heartbeat, and difficulty breathing.
Step-by-step explanation:
The most serious heat-related medical condition resulting in the need for immediate medical attention is heat stroke. Heat stroke is a life-threatening condition that occurs when the body's temperature regulation system fails and body temperature rises to a dangerous level. Symptoms of heat stroke include a high body temperature, altered mental status, hot and dry skin, rapid heartbeat, and difficulty breathing.