Extreme heat poses challenges across the world, but heat-related deaths are largely preventable. Our Network’s efforts to save lives are driven by the following key messages:

Heat stress is a serious and urgent health threat for humans.

It is a leading cause of weather-related death, and can result in permanent damage to the brain, central nervous system, and other internal organs exacerbating cardiovascular, respiratory, and psychological distress, injuries, and infectious disease.

Extreme heat waves are invisible disasters.

Similar to hurricanes, tsunamis, and earthquakes, they can result in significant mortality and morbidity, as well as economic damages and destruction of property that can overwhelm response systems. Dangerous heat conditions can also manifest during heat spells outside the hot season, prolonged periods of locally relevant elevated daytime and night time thermal conditions, and in specific microclimates.

Heatwaves are increasingly accompanied by cascading environmental or socio-economic impacts from heat triggered wildfires and drought to food, energy, water, and transport infrastructure failures. The true global scale and magnitude of the impacts of heat on society are recognized to be under-reported and underestimated.

All populations are affected by rising ambient temperatures.

However, some populations are more vulnerable to heat stress and increased risk of death or illness due to a combination of high exposure, physiological preconditions and socioeconomic status. These include the rural and urban poor, populations in regions that are already very hot and humid, regions with colder climates that are facing warmer summers, older adults, infants and children, pregnant women, indoor and outdoor labourers, athletes, attendees of outdoor events, and those with some pre-existing medical conditions.

Occupational heat strain directly affects workers’ health.

Impacts include elevated risk of dehydration, kidney disease, work accidents, and lost work productivity. Heat may be indirectly influencing global health in significant ways, as the loss of productivity and income hinders individual ability to live healthy and productive lives.

Urban environments magnify heat exposures.

This is due to dense and vertical constructions, extensive use of heat retaining materials, limited vegetation cover, and heat generation from energy use in cooling and transport, that all contribute to urban heat island effects. Urban Heat Islands, and micro-heat islands within cities, increase exposure risk to local inhabitants.

The mental health impacts of heat are an emerging area of interest.

Heat influences brain functioning and behaviour, and people with mental health issues and/or prescribed medications which limit the body’s natural cooling functions are especially vulnerable. Social connectivity is important for risk reduction.

Heat-related problems are destined to increase for decades to come.

This is due to greenhouse gases already in the atmosphere that are rapidly warming the earth’s climate. The degree and rate of future warming and impacts beyond 2100 will depend on the success of climate change mitigation efforts. Taking appropriate action and preparedness to face a warming world is imperative and urgent.

Key Messages and Priorities for Specific Contexts

Call to Action

Learn more about solutions, challenges, and our action agenda.