Heat Action Day 2025

The “summer of the century” is looming in 2025: Heat is no longer a marginal issue, but the greatest climate-related health risk in Germany. Today, June 4th, is the nationwide Heat Action Day – an occasion to highlight the dangers of heatwaves, the importance of heat protection, and the role of urban greenery and innovative solutions.

Heat Action Day 2025: Heat Protection for All

This year’s action day is themed “Heat Protection for All”. The goal is to raise awareness of the health risks posed by heat and to focus on concrete protective measures. Heat “can be dangerous for everyone, and the risk will continue to increase in the coming years” – but especially vulnerable groups such as the elderly, infants and children, pregnant women, the sick, or the homeless are most at risk.

Photo: Heat Action Day

Heatwaves and Urban Heat Islands: The Invisible Danger in Our Cities

Last year, the German Environmental Aid (Deutsche Umwelthilfe, DUH) announced: “Many German cities failed the first heat check.” Cities are undoubtedly the living spaces of the future. However, urban areas heat up particularly strongly due to dense construction, sealed surfaces, and a lack of greenery. Globally, 80% of cities are facing extreme climate-related events.

Extreme heatwaves have become a defining feature of summers worldwide. As global temperatures continue to rise, these events are becoming more frequent, intense, and prolonged. According to an analysis by World Weather Attribution, heatwaves are now 30% more likely due to climate change. The existing “lack of heat protection” is already costing Germany billions of euros annually, says Martin Herrmann, Chair of the German Alliance on Climate Change and Health (Deutsche Allianz Klimawandel und Gesundheit).

The so-called urban heat island effect means that city centers are often several degrees warmer than surrounding areas. This creates hotspots that pose significant health risks to the population – especially for older people, children, pregnant women, and those with chronic illnesses.

The Consequences Are Dramatic:

• According to the Federal Ministry of Health (Bundesgesundheitsministerium), thousands of people die each year in Germany as a result of extreme heat. Just yesterday, the Federal Environment Agency (Umweltbundesamt) published the latest four-year analysis on heat-related mortality in Germany, commissioned by the Federal Ministry for the Environment and prepared by the Robert Koch Institute (RKI): “It was found that in the summers of 2023 and 2024, there were about 3,000 heat-related deaths in Germany each year. Those most affected were people over 75 with pre-existing conditions such as dementia, cardiovascular, or lung diseases.”
• Symptoms range from circulatory problems, dizziness, and exhaustion to dehydration and life-threatening heat strokes.
• The medical journal Ärzteblatt and the platform “Plattform Klima Mensch Gesundheit” warn: Heat is often underestimated, but the risks are real and are increasing with climate change.

„Due to climate change, the problem of excess mortality in summer will become even more severe in the future,” UBA President Messner is quoted as saying.

Photos: Moritz Ludke via Unsplash & Federal Environment Agency

Heat Protection: What Cities and Policymakers Can Do Now

Heat Action Day is initiated by the German Medical Association and the German Alliance on Climate Change and Health (Deutschen Allianz Klimawandel und Gesundheit e.V., KLUG) and is supported by a broad alliance of healthcare, social organizations, municipalities, and other stakeholders. The initiators are calling for binding heat protection plans, more public drinking water stations, cool retreats and better public education. It is particularly emphasized that heat protection is a societal responsibility and must not be limited to the healthcare sector.

Responses are happening, but often too slowly. The Federal Ministry of Health has presented new and expanded heat protection plans that call for binding nationwide measures. Cities like Jena (“the warmest city in Thuringia”) and Dortmund are already implementing dynamic action plans, ranging from drinking water fountains to cool retreats and awareness campaigns. The Berliner Senate is planning a heat action plan. The German Environmental Aid (DUH) is calling for a master plan for heat protection in all cities.

But how can cities truly become cooler in a sustainable and efficient way?

Source: City of Dortmund “Cool Places Map”

Urban Greenery: The Natural Air Conditioner

„“Health-related heat protection must be integrated into all infrastructure, construction, and urban development measures. Climate protection as the most important health project of our time must be given top priority”, says Dr. Martin Herrmann, Chair of KLUG e.V.

Green infrastructure is a key to reducing heat in cities. Parks, trees, green facades and green roofs lower ambient temperatures, improve air quality, and promote health. Urban greenery, for example, can mitigate the effects of global warming and urbanization. An “expansion of green infrastructure” and the resulting urban green spaces are “perhaps the most efficient and intuitive way to reduce urban heat island effects and provide comfort for nearby residents”.

The World Economic Forum has pointed out that “nature is the most resource-efficient solution for creating resilient, vibrant, and future-proof cities”. But that’s not all: As early as 2021, a “groundbreaking study” by the International Institute for Sustainable Development (IISD) found that “using nature in infrastructure projects could save$248 billion per year”!

Barbara Metz, Federal Managing Director of the German Environmental Aid (Bundesgeschäftsführerin der Deutsche Umwelthilfe), also emphasizes the need for “mandatory shares of green and blue infrastructure that must be firmly anchored in urban planning. Particularly vulnerable groups such as residents in care facilities, schoolchildren, and children in daycare centers need targeted protection from heat”.

What do nature-based solutions look like? It’s not about a single measure, but many different ones.

Photos: GCS

How to Efficiently Create Cool Spaces as Temperatures Rise

Mosses are true climate protectors. They bind fine dust, cool through evaporation, and improve air quality. Green City Solutions leverages these properties in innovative moss filters, which can be specifically deployed at urban heat hotspots. These filters lower ambient temperatures, filter pollutants, and create noticeably better comfort – even in highly stressed locations.

Since summer 2022, we have been conducting initial tests and comparisons using a FLIR thermal imaging camera, an infrared thermometer, and the integrated sensors in the CityTree, both outdoors in Bestensee (Brandenburg) and in the Italian city of Bari. During the summer months, we already experienced several heatwaves with temperatures above 40°C, but the moss filter always emitted a pleasantly cool breeze – clearly noticeable. Various measurements confirmed significant temperature differences, even compared to the surface temperature of nearby vegetation.

Photos: GCS

Bio-digital Innovations Combine Moss with Smart Technology

They filter fine dust, cool the environment, and provide real-time air quality data. This creates green oases in the heart of the city, improving not only the climate but also people’s well-being.

Heat Protection Is Urban Development – and It Starts Now

The research is clear, the solutions are available – now cities must act. Urban greening, innovative moss filters, and targeted heat protection measures are the key to livable, healthy cities of the future. Heat Action Day 2025 is the perfect occasion to take responsibility together.

Excursus: Heat Protection in Companies and the Real Estate Sector

While municipalities are working to implement their legal obligations to protect the public from heat, companies are facing additional challenges: Energy costs for conventional air conditioning and cooling are rising – as are the requirements for the working environment. Appropriate quality-enhancing measures should be taken, affecting both general working conditions (e.g., in production halls) and the design of recreational areas (e.g., in canteens).

This also presents a challenge for another sector. The real estate industry must ensure that compensation areas and legal requirements are considered in the design and realization of projects, in order to maintain the attractiveness of properties for users.

Photos: GCS