Topic Overview

Signs of rapidly progressing heatstroke include:

• Unconsciousness for longer than a few seconds.
• Convulsion (seizure).
• Signs of moderate to severe difficulty breathing.
• A rectal temperature over 40°C (104°F) after exposure to a hot environment.
• Confusion, severe restlessness, aggressive behaviour or anxiety.
• Fast heart rate.
• Sweating that may be heavy or may have stopped.
• Skin that may be red, pale, hot, and dry, even in the armpits.

Signs of heat exhaustion that may also quickly lead to heatstroke:

• Nausea, vomiting or diarrhea. 
• Headache, dizziness or feeling faint. 
• Weakness or muscle cramps, usually in the legs and abdomen. 

After calling 911 or other emergency services, begin emergency first aid treatment if emergency medical personnel (such as paramedics) are not going to arrive soon.