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 9-1-1 or other emergency services, begin emergency first aid treatment if emergency medical personnel (such as paramedics) are not going to arrive soon.