Better Heat Planning Can Protect Crowds and Ease Pressure on Hospitals, WHO Says

The review examined studies published between 1980 and 2025, documenting nearly half a million medical encounters at mass gatherings, including more than 22,000 heat-related illnesses.

Heat-related illness is becoming a serious concern at major sporting, religious and cultural events, where spectators, attendees, volunteers and workers can face hours of exposure to high temperatures and crowded conditions. A new World Health Organization (WHO) evidence review and accompanying guidance show that most heat-related illnesses at these gatherings can be prevented or treated at the venue when organizers put timely risk management measures in place, protecting people and reducing pressure on surrounding health services.

What the evidence reveals about care at event venues

The review examined studies published between 1980 and 2025, documenting nearly half a million medical encounters at mass gatherings, including more than 22,000 heat-related illnesses. Studies showed that well-organized on-site medical systems could treat more than 90% of patients at event venues, substantially reducing demand on local hospitals and ambulance services. These findings underline the value of preparing medical teams and treatment facilities before an event begins, giving people access to care without automatically requiring a hospital transfer.

Dr Chikwe Ihekweazu, Executive Director of WHO's Health Emergencies Programme, described extreme heat as a threat to health, safety and the ability to keep events running, calling for it to be treated as a central responsibility in event operations and governance. His message places responsibility beyond the individual attendee: personal precautions need support from consistent risk assessment, preparedness and response systems that reduce immediate harm and make event planning more resilient in a warming world.

Why large gatherings make heat exposure more dangerous

The wider health burden is substantial, with an estimated 63% increase in heat-related deaths since the 1990s and an average of 546,000 deaths annually between 2012 and 2021. The Intergovernmental Panel on Climate Change reports that hot extremes, including heatwaves, have become more frequent and intense across most land regions since the 1950s, mainly because of climate change. Every additional increment of global warming is projected to bring further increases in their frequency and intensity, making heat preparedness an increasingly important part of planning large events.

People at mass gatherings can face several risks at once, from prolonged exposure to sun and heat to dense crowds and limited access to safe drinking water. Travel-related stress and unfamiliarity with the local climate can make conditions harder to manage, particularly when health services are already handling competing demands. The danger depends on how an event is organized, because venue layouts, transport arrangements and crowd movement influence whether people can reach water, cooling facilities and medical help when they need them.

Making heat protection part of the entire event

WHO's new resources, titled Prevention and management of heat-related illness at mass gatherings, draw on evidence synthesized through systematic reviews and lessons from events worldwide. The findings support investment before temperatures become dangerous, combining accessible safe drinking water and toilets, cooling infrastructure, schedule adjustments, crowd-flow management, workforce protection, public communication, real-time surveillance and well-prepared on-site medical services. Together, these measures support spectators, attendees, volunteers and workers through arrangements that make protection and treatment easier to access.

The guidance takes a whole-of-event approach covering venue design, crowd management, water and sanitation, transport, security, communications and workforce management throughout the full event cycle. It complements WHO's guidance on heat-health action plans, national heat-health plans, occupational health and safety requirements, emergency preparedness arrangements and clinical guidance. WHO is calling on governments, event organizers and partners worldwide to integrate heat risk management into health planning, preparedness and daily operations, embedding these measures within broader emergency planning and systems that address all types of hazards.