Heat Exhaustion – excerpt from MayoClinic.com

Definition:  Heat exhaustion is a condition whose symptoms may include heavy sweating and a rapid pulse, a result of your body overheating.  It’s one of the three heat-related syndromes, with heat cramps being the mildest and heatstroke being the most severe.

Causes of heat exhaustion include exposure to high temperatures, particularly when combined with high humidity and strenuous physical activity.  Without prompt treatment, heat exhaustion can progress to heatstroke, a life-threatening condition. Fortunately, heat exhaustion is preventable.
 
Symptoms

Signs and symptoms may come on suddenly or may develop after days of heat exposure. Possible heat exhaustion signs and symptoms include:

• Cool moist skin with goose bumps when in the heat
• Heavy sweating
• Faintness
• Dizziness
• Fatigue
• Weak, rapid pulse
• Low blood pressure upon standing
• Muscle cramps
• Nausea
• Headache