Europe has spent much of this summer learning just how dangerous extreme heat can be. Four successive heatwaves swept across the continent, with around 80 million Europeans experiencing temperatures of 40°C or higher. Provisional estimates suggest that at least 35,000 additional deaths occurred during the heatwaves, with Germany, France and Spain alone accounting for more than 25,000. The final toll is expected to rise as national mortality data are completed.

These numbers are shocking. They should not, however, be entirely surprising. Europe has known for decades that extreme heat kills. The heatwave of 2003 was estimated to have caused around 70,000 deaths across Europe. The lesson from that disaster was supposed to be preparedness. Countries introduced heat-health warning systems, emergency protocols and other adaptation measures. Yet the deaths continue on a massive scale.

In June, the World Health Organisation said that more than 200,000 people had died from heat across the European Union and associated countries over the previous four years. WHO Regional Director Hans Henri Kluge described most of these deaths as preventable and warned that the mortality figures represented only "the tip of the iceberg", with millions more people experiencing physical and mental health effects.

The problem no longer appears to be simply that Europe is becoming hotter. It is that heat is becoming a persistent medical challenge for European societies.

A 2024 study published in Nature Medicine found that without the adaptation measures introduced since the beginning of this century, the heat-related mortality burden would have been approximately 80 per cent higher. Among people aged over 80, it would have been more than twice as high. That finding contains both a warning and a reason for optimism. Adaptation works. Heat warnings, better healthcare, changes to buildings and public awareness save lives. But adaptation is being asked to run increasingly fast simply to keep up with a climate that is changing even faster.

And the medical consequences of heat extend far beyond the familiar image of someone suffering from dehydration or heatstroke. The World Health Organisation warns that extreme heat can worsen cardiovascular disease and other pre-existing conditions, while older people, infants and those with chronic illnesses are particularly vulnerable.

New research published makes the picture even more striking. Researchers at Northwestern University examined almost one million emergency-department and urgent-care visits in Chicago and identified 33 diagnoses associated with extreme heat. These included acute kidney failure, skin conditions, multiple sclerosis, mental and behavioural disorders, insect bites and various injuries.

The significance is not that every one of these conditions is caused directly by heat. Rather, it demonstrates how easily the health burden of extreme temperatures can be underestimated when doctors and health authorities only look for conventional "heat-related" illnesses. Heat can aggravate existing disease, place additional strain on the heart and lungs, disturb sleep and mental wellbeing, and increase pressure on emergency services. Some effects may only become apparent days after exposure. This matters particularly for an ageing Europe.

The European Environment Agency identifies heat as the deadliest of Europe's weather- and climate-related hazards. Yet it also notes that Europe still lacks a continent-wide system capable of recording heat-related deaths and illness in real time. In many countries, the true mortality burden is therefore calculated retrospectively through epidemiological models.

Malta provides a particularly stark example. During the peak of July's heatwave, when the island experienced three consecutive days above 42°C and a record July temperature of 43.3°C, 20 deaths were recorded as directly or indirectly related to heat between 20 and 26 July. The people who died were aged between 55 and 89. Initial hospital data also showed that 179 people sought emergency assistance because of the heat.

The numbers may not capture the full impact. Malta's health authorities themselves acknowledged that heat may have contributed to the deterioration of pre-existing conditions in patients whose deaths were not specifically classified as heat-related. And the experience of the heatwave exposed another vulnerability: infrastructure. Malta suffered prolonged power cuts during the period of extreme temperatures, potentially depriving households of one of their most important defences against heat: cooling.

This brings us to a question that is increasingly difficult to avoid: when extreme heat becomes foreseeable, who is responsible for protecting people from it?

One answer came from Strasbourg in 2024. In Verein KlimaSeniorinnen Schweiz and Others v Switzerland, the European Court of Human Rights considered the case brought by an association of older Swiss women and four individual applicants who argued that inadequate climate action was exposing them to serious health risks from increasingly severe heatwaves.

Their experiences put a human face on the statistics. One applicant had collapsed during heatwaves and had required hospital treatment. Another described having to organise her entire life around the weather, remaining indoors with the blinds closed and air conditioning running during periods of extreme heat. A third suffered aggravated asthma and chronic obstructive pulmonary disease and had to restrict her activities.

The Court ultimately held that Switzerland had violated Article 8 of the European Convention on Human Rights, which protects the right to respect for private and family life, because it had failed to fulfil its positive obligations concerning climate change. The judgment was significant because it recognised that effective protection against the serious adverse effects of climate change falls within the Convention's protection of human rights.

The judgment does not mean that every heat-related death automatically amounts to a human-rights violation. Nor does it make governments responsible for controlling the weather. It does, however, establish an important principle: governments cannot treat climate-related threats to health as entirely beyond their responsibility when the risks are known and foreseeable.

This is ultimately what makes Europe's increasingly hot summers different from an ordinary heatwave. The heat itself may be a physical phenomenon, but the number of people exposed to it, the vulnerability of our ageing populations, the design of our homes and cities, the resilience of electricity grids and healthcare systems, and the speed at which governments cut emissions are all matters of policy.

The question is therefore not whether Europe can survive another hot summer. It is whether European governments are prepared to accept tens of thousands of deaths as the price of increasingly extreme heat when the evidence tells us that many of those deaths can be prevented.

Lina Klesper is International Legal Assistant at PKF Malta