“…[7][8][9] The Hajj is regarded as the best mass gathering preparedness effort worldwide; nevertheless, the history of the Hajj is replete with heat illnesses. Major contributors to overall heat stress are mean temperatures reaching 45°C, humidity approaching 80%, and stagnant atmospheric conditions potentiated by heat dissipation from asphalt and concrete surfaces, vehicle exhaust, Hajj crowds, and human activities.…”