Heat Stroke Timeline: How It Can Develop

Early heat illness may cause thirst, heavy sweating, tiredness, dizziness, headache, cramps, or nausea. Without effective cooling, dehydration and rising body heat can impair thinking and movement. Heat stroke is marked by a dangerous rise in temperature together with brain or nervous-system changes such as confusion, fainting, seizure, or unusual behaviour. A person may stop sweating, but sweating can also continue, so skin moisture does not rule it out.

Stop exertion and move the person to a cooler environment at the first signs of heat illness. Remove excess clothing, wet the skin, and increase airflow. If confusion, collapse, seizure, or severe weakness appears, call emergency services immediately and continue cooling while waiting. Keep monitoring breathing and stay with the person; do not leave them to recover alone.

Get urgent medical help if symptoms worsen, do not improve promptly with cooling, or include vomiting, fainting, confusion, seizure, or trouble walking. Do not use a symptom-free interval after rest as proof that serious heat illness has resolved. Fever can resemble overheating, and a clinician can assess both possibilities.

Ask how long to avoid heat and strenuous activity, how to resume fluids and exercise, and whether any ongoing weakness, muscle pain, or dark urine needs assessment.