Extreme heat has become one of the most pressing public health threats today, with their intensity, duration and frequency increasing due to climate change. In the World Health Organization (WHO) European Region, heat is the deadliest natural hazards. Add to this the trend of an aging population and massive urbanization, and you have a „perfect storm“ of vulnerability that requires systematic and long-term solutions.

In response to these developments, WHO has issued a second, updated edition of guidelines for Action plans Heat Health Action Plans (HHAP), which provide states and local governments with an implementation-oriented framework for preventing deaths and illnesses.

Health impacts: Direct and indirect threats

In extreme temperatures, the human body loses its ability to regulate its internal temperature, which places a huge strain on the heart and kidneys. Extreme heat has direct impacts, including dehydration, heat exhaustion, and life-threatening heatstroke. It also rapidly worsens existing chronic diseases, especially cardiovascular, respiratory, and kidney diseases, as well as diabetes and mental illness.

The indirect effects of heat are equally serious. They include enormous strain on hospitals and emergency services, disruptions to electricity and drinking water supplies, and an increased risk of accidents and work-related injuries.

Who is most at risk?

Heat does not affect the entire population equally. Vulnerability is determined by physiological sensitivity, the level of exposure and the ability of the individual to protect themselves. Priority groups that action plans must target include:

• Older people: Aging weakens thermoregulation and the sense of thirst, which increases the risk of dehydration. Many older people suffer from comorbidities and take medications (e.g. diuretics, antihypertensives, or psychotropic drugs) that can reduce heat tolerance.
• Pregnant women, newborns and children: For pregnant women, heat increases the risk of complications, including premature birth. Young children and newborns do not have fully developed thermoregulation and are completely dependent on adults.
• Workers: People performing heavy physical work outdoors (construction, agriculture) or in hot and poorly ventilated interiors face a massive risk of health damage and increased accident rates.
• Socially disadvantaged persons: People living in social isolation, the homeless, or those living in poorly insulated apartments without access to cooling (energy poverty) are among the most vulnerable groups in cities.

WHO's Eight Essential Elements of Protection (HHAP)

Heat Hazard Action Plans (HHAPs) are designed to move heat management from ad hoc measures to predictable and coordinated action. A modern plan should include 8 key elements:

1. Governance: The plans require strong political leadership and a clear inter-ministerial division of tasks to make the measures work at national, regional and local levels.
2. Early warning systems: Weather warnings must be linked to specific, predefined health measures. Ideally, thresholds are graded and take into account local climatic conditions.
3. Protection of populations at increased risk: It is essential to actively identify and protect the vulnerable, for example by linking health and social services to ensure active detection and screening of at-risk individuals.
4. Communication: Information must be credible, targeted and focused on specific action, thereby encouraging the public to adopt adaptive behavior.
5. Health system resilience: Healthcare must manage extremes. This means preparing staff, protecting workers from the heat, building cool zones in hospitals, and ensuring backup power sources and safe refrigeration of medications.
6. Reducing heat exposure: It requires collaboration beyond healthcare – it includes passive cooling of buildings, green infrastructure and smart urban planning.
7. Health monitoring (Surveillance): Active monitoring of mortality, morbidity, and ambulance departures in real time is key to timely adjustment of emergency measures.
8. Monitoring, evaluation and learning: After each season, reflection must come. The data obtained serves to adjust warning thresholds, communication strategies, and the overall plan.

Cities and buildings as the first line of defense

In cities, heat intensifies the effect of the so-called urban heat island, where concrete, asphalt and lack of greenery absorb heat during the day and release it at night, preventing the body from naturally regenerating. The healthcare sector cannot solve this alone – the connection with urban planning is key.

Cities must invest in green and blue infrastructure (trees, parks, water features) which provides natural shading and reduces local temperatures. At the building level, WHO recommends prioritizing passive cooling strategies. These include high-quality insulation, night ventilation of buildings, external shading (blinds, shutters) and the application of "cool" or green roofs.

Although it is active air conditioning (AC) important and often „life-saving“ technology for vulnerable groups of the population, from a global perspective it is an unsustainable solution in the long term. Air conditioning worsens urban heat islands by releasing hot air and contributes to the climate crisis through high energy consumption. Access to cooling should be addressed fairly, with municipalities ensuring public cooling centers and accessible drinking water in public spaces.

Practical steps for the public: #KeepCool campaign

Educating the population can save many lives. WHO communication campaigns focus on three basic pillars of protection in homes, schools and the workplace:

• Keep your home cool: Ventilate especially at night and early in the morning when the air is cooler. During the day, close windows and draw curtains or external blinds to prevent sunlight from entering. Turn off electrical appliances that generate excess heat.
• Cool your body and drink water: Drink clean water regularly, even when you don't feel thirsty (2-3 liters per day is recommended, depending on your activity and health). Avoid sugary, caffeinated, and alcoholic beverages, which dehydrate you. Take cool showers or apply wet towels, and wear light, breathable clothing.
• Avoid heat: Limit strenuous physical activities outdoors, ideally moving them to the morning or late evening. Seek shade and spend at least 2-3 hours in a cool room during the hottest hours. Never leave children or animals in a parked car.
• Stay in touch and help: Check daily on elderly and sick family members or neighbors who live alone and may need help coping with the heat.

Extreme heat events are becoming more intense due to climate change and growing cities. However, if they are addressed systematically through high-quality Heat Hazard Action Plans (HHAPs), functional warnings are implemented, and cities are rebuilt to be more resilient, we can successfully prevent almost all heat-related deaths and acute health crises. JRi&CO2AI