The impacts of heat on health: surveillance and preparedness in Europe

Why is it important to monitor heat impacts on health?

In recent years, Europe has experienced record-breaking summer temperatures and repeated, long-lasting heatwaves (ECMWF, 2022; C3S, 2024a). When exposed to periods of very high temperature, the human body may struggle to regulate itself, resulting in heat stress, heat exhaustion, heat stroke and complications from pre-existing medical conditions, in some cases leading to premature death. Elderly people, children, pregnant women, outdoor workers, people suffering from cardiovascular, respiratory or renal diseases, diabetes or mental health disorders and marginalised and under-resourced people are among the most vulnerable to extreme heat (WHO Europe, 2021).

Heat impacts also are an additional burden for Europe’s already stretched healthcare systems. For example, in Portugal, daily hospital admissions increased by 19% during heatwave days between 2000 and 2018 (Alho et al., 2024). In France, in 2022, emergency department visits doubled and consultations with physicians tripled during heatwaves for three health conditions linked to high temperatures — hyperthermia, dehydration and hyponatremia — compared to non-heatwave conditions (Sante Publique France, 2022). Whilst very high summer temperatures also have other implications for human health — e.g. via increased risk of some food-borne diseases (EFSA, 2020) or wildfires — this briefing focuses only on the direct impacts of heat.

As many as 95% of the fatalities associated with weather and climate-related extremes recorded in Europe between 1980 and 2023 were linked to heatwaves (EEA, 2024b). Extremely high temperatures are projected to increase in frequency in the future. Even if global warming is limited to the 1.5°C level, 100 million people in the EU and the UK are expected to experience extreme heatwaves annually by the end of the century; a tenfold increase compared to the 1981-2010 baseline (Naumann et al., 2020). The effects of global warming are already being felt now: half of the heat-related deaths in Europe in the summer of 2022 have been attributed to anthropogenic climate change (Beck et al., 2024). Other factors — such as an ageing population, the growing prevalence of chronic diseases and ongoing urbanisation — are increasing the risks of heat-related health impacts in Europe (EEA, 2022). The European Climate Risk Assessment describes the current level of risk to human health from heat as ‘critical’, growing to ‘catastrophic’ in the second half of the century, calling for urgent action (EEA, 2024a).

Whilst heat stress is obviously damaging to human health, there is no near-real time record keeping system of heat-related deaths and health impacts at the European level. Therefore, it is difficult to track how many people die from heat or how many people’s health is affected by heat across Europe. Rather, weekly and monthly estimates of excess deaths from all causes above a five-year baseline are provided by Eurostat (2023, 2024). To establish the link between deaths and heat, epidemiological models tend to be applied retrospectively to temperature and mortality records. For example, for 2022, it was estimated that over 60,000 people in Europe died from heat (Ballester et al., 2023); this figure was later updated to over 70,000 (Ballester et al., 2024). In 2023, just under 48,000 heat-related deaths were estimated across Europe (Gallo et al., 2024).

Deploying emergency response measures during periods with very high temperatures as well as having long-term adaptation actions in place is central to reducing heat-related deaths and illnesses. Accurate and timely data on the health impacts of heat is critical for designing and implementing these measures. In addition to collecting data on deaths, it is essential to collect data on heat-related morbidity, such as dehydration, hyperthermia, or worsening of symptoms of existing diseases. This data allows for the full scope of the health impacts of heat to be understood and enables targeted measures to be deployed to counteract them. Further, baseline information about the number of heat-related deaths and health effects allows assessment of whether the preventative measures used have been effective in reducing impacts.

This briefing maps the surveillance of heat-related health impacts and the existence of heat-health action plans (HHAPs) in European countries, drawing on the results of a 2024 survey issued to national public health institutes (NPHIs) in the EEA’s member and cooperating countries (Box 1). More detailed survey findings can be found in the technical report (European Climate and Health Observatory, 2024). The briefing also integrates findings from a survey on HHAPs conducted by the World Health Organization (WHO) Regional Office for Europe in 2019 (WHO Europe, 2021) and draws on a study on heat-health warning systems (Casanueva et al., 2019).

Surveillance of heat-related mortality and morbidity in Europe

Defining ‘heat’ and ‘heatwaves’

In this briefing, for simplicity, the terms ‘heat’ or ‘high temperatures’ are used to describe thermal conditions that result in increased risk of health impacts for people. In the scientific literature, deaths attributable to heat and deaths attributable to heatwaves are distinguished. Deaths attributable to heat are understood as those linked to temperatures above the minimum mortality temperature (i.e. the optimum temperatures associated with the lowest number of deaths) whereas deaths from heatwaves refer to mortality from extremely high temperatures occurring during periods defined by authorities as a heatwave. These two numbers can differ considerably; for example, in France approximately 29% of deaths attributable to heat between 2000 and 2010 were due to extreme temperatures observed during heatwaves and 71% of deaths were due to usual summer heat (Pascal et al., 2024).

There is no standard definition of the terms ‘heat’ and ‘heatwave’ in Europe (C3S, 2024b). Diversity of climatic conditions, demography and other vulnerability factors, such as urbanisation, together with different levels of acclimatisation to heat in the population mean that heat-related deaths and health impacts increase at different temperature thresholds across Europe (Masselot et al., 2023).

The results of the survey conducted with NPHIs show the range of ways in which heat and heatwaves are defined. The national definitions of ‘heat days’ include days exceeding certain maximum daily temperatures (e.g. 26°C in Sweden, 28°C in Belgium and 30°C in Cyprus); or daily mean temperatures over a certain threshold (e.g. 20°C over the course of 24 hours in Germany); or apparent temperatures/thermal comfort indices that take account of humidity (European Climate and Health Observatory, 2024).  

’Heatwaves’ were most commonly but not uniformly defined as at least three to five consecutive days with daily maximum temperatures above various thresholds (e.g. 30°C in Austria, 28°C in Norway, 99.5th percentile of the 1980-2010 temperature distribution in France and exceeding the average maximum temperature of the month by 5°C or more in Malta). Italy is the only country to define a heatwave in a way which takes account of the effects of heat on health, as three consecutive days with heat warnings, issued when excess in mortality due to heat is predicted to exceed 20% (European Climate and Health Observatory, 2024). This variability, whilst justified from the perspective of individual countries, presents a challenge for aggregating or comparing data on the health impacts of heat at the European level.

An overview of surveillance of heat-related impacts on health in Europe

Among the 28 NPHIs that responded to the 2024 survey, 17 have a surveillance system in place to forecast, monitor and/or evaluate the impact of heat on health. Four more NPHIs are in the process of developing such a surveillance system. In a 2019 pan-European study, three additional European countries were identified as having a surveillance system in place (Casanueva et al., 2019). Thus, in total, a surveillance system for heat-related health impacts exists in 20 out of the EEA-38 countries. Nearly all of the seven countries that stated in the 2024 survey that they did not have a surveillance system were in eastern Europe (Map 1).

Heat-health surveillance systems across Europe reflect country-specific needs and contexts. For example, country-level surveillance systems in Europe are activated for a range of periods— anywhere from two months over the summer to the entire year. They collect mortality and morbidity data for regions of varying sizes, and break the data down according to various age groups and in most cases gender (see details in the European Climate and Health Observatory, 2024). The variety of surveillance approaches, combined with the absence of monitoring in several countries, makes it difficult to obtain a complete picture of the health impacts of heat at the European level in near real-time.

Forecasting, monitoring and evaluating heat impacts on health

Under the umbrella of surveillance for the health impacts of heat, three complementary approaches were explored in the NPHI survey: (1) forecasting the impacts before they occur to mobilise resources and prepare for action; (2) monitoring the impacts during periods of heat and heatwaves to support rapid decision-making to prevent adverse health impacts; and (3) evaluation of the health impact of heat after hot periods have occurred to support longer-term decision-making.

Forecasting health impacts before periods of hot weather

Anticipating the possible scale of health impacts can be used to prepare for upcoming periods of hot weather — for example, by informing the public, ensuring that social care institutions are prepared, and that emergency rooms are staffed with extra personnel. According to the survey, eight NPHIs use weather forecasts to predict heat-related health impacts (European Climate and Health Observatory, 2024); heat-health early warning systems were also noted in North Macedonia, Portugal and Slovenia (Casanueva et al., 2019).

In Italy, a heat health watch warning system has been in place since 2004. This system monitors the health impacts of heat in regional capitals and cities with a population of over 200,000. Risk levels are based on the relationship between temperature and expected excess mortality. In Spain, heat risk is forecast for 182 ‘isoclimatic’ or Meteoalert zones, predefined by the Spanish national meteorological agency (European Climate and Health Observatory, 2024).  While the Portuguese NPHI did not respond to the survey, the country’s national heat-health warning system, ÍCARO, is well known for its role in keeping people safe from extreme heat. It is designed to produce a daily report with heat-related mortality predictions, which is shared with practitioners involved in implementing measures under the HHAPs (Leite et al., 2020).

Real-time monitoring of the health impacts of heat

Monitoring heat-related deaths and morbidity in real time is critical for rapid decision-making such as activating or adjusting emergency health system responses. According to the survey, 13 NPHIs collect near real-time data on heat-related deaths during predefined heatwaves and periods of heat. Morbidity data associated with heat are collected by NPHIs in seven countries and include emergency room visits (five countries), ambulance calls (five countries), GP consultations (five countries) and hospital admissions (three countries), either for all causes or for specific diseases and related health problems (European Climate and Health Observatory, 2024). Countries also rely on modelled or expected impacts from heat-health warning systems to support rapid decision-making during heat waves (Casanueva et al., 2019).

Evaluating the impact of heat on health post factum

12 countries stated that they evaluate the impacts of heat on health retrospectively, with most of them focusing on mortality rather than morbidity data. NPHIs apply various modelling techniques to estimate heat attributable deaths and then analyse and communicate the deaths associated with heat over a given period.

Implications

The surveillance of the health impacts of heat is central to the public health response to this climate hazard. Just over a quarter of the responding countries forecast heat-related mortality and fewer than half monitor heat-related deaths in near-real time. The lack of timely data in the remaining countries can be regarded as an obstacle to timely and effective action against heat-related deaths.

Additionally, the low number of countries tracking heat-related morbidity indicates that there is a continuing emphasis on recording deaths during periods of heat. Yet, a better understanding of the effect of heat on the use of healthcare services could help public health authorities to target appropriate interventions to reduce the current and future health burden (Boudreault et al., 2024).

Data on the health impacts of heat is also essential for the long-term development of public health policies, selecting adaptive measures and planning for future heat-related impacts on human health and healthcare systems. These data may help to ensure that climate adaptation measures — such as increasing the percentage of green space (in particular trees), improved building design, implementing district cooling systems or adapting working conditions to avoid heat — are prioritised.

Heat-health action plans

HHAPs are recognised as a key tool for reducing deaths and preventing other health impacts during periods of high temperatures (WHO Europe, 2021; IPCC WGII, 2022). The purpose of a HHAP is to assign responsibilities in the event of a heat emergency, as well as to plan both short-term actions (such as issuing weather-based alerts and advice on behaviour) and long-term improvements in housing and urban planning to reduce heat exposure (WHO Europe, 2021). HHAPs tend to focus on vulnerable groups; they also ensure that healthcare and social systems are ready to act in the event of extreme heat (Climate-ADAPT, 2021).

Status of heat-health action planning in Europe

According to the 2024 survey, 12 of the 28 responding NPHIs have HHAPs in place at either the national, regional or local level, while four more are in the process of developing HHAPs. A 2019 survey found that nine additional European countries have implemented HHAP at the national, regional or local level (WHO Europe, 2021). Combining those results, the presence of HHAPs has been confirmed in 21 of the EEA-38 countries, while 10 NPHIs have stated not having such plans (see Map 2). However, as the 2024 survey addressed NPHIs, it cannot be excluded that some countries have HHAPs developed by other institutions.

HHAPs exist at different and sometimes multiple administrative levels, reflecting each country’s governance structure and the level at which the responsibility for health impact prevention lies (see Table 1). In Belgium, for example, the Brussels, Flemish and Walloon regions have separate HHAPs. A similar set-up is also seen in Italy, whereas in the Netherlands, 40 cities have each developed their own HHAPs. In Hungary, specific recommendations have been developed for certain groups or sectors, such as for child and social welfare institutions.

Implications

Over a quarter of countries in Europe do not have HHAPs, which may negatively impact their preparedness to heat. According to some studies, HHAPs have been effective in keeping people safe during periods of high temperatures. For example, after the introduction of a national heat plan in Italy, the impact of extreme temperatures on mortality has declined (de’Donato et al., 2018). Germany’s national HHAP has also been credited with improving heat-health outcomes (Matzarakis, 2017). However, not many evaluations of the impact of HHAPs on mortality have been made — and even fewer are available for morbidity outcomes (Dwyer et al., 2022).

Furthermore, despite the activation of HHAPs by many European countries during the summer of 2022, the widely accepted estimate of more than 60,000 heat-related deaths suggests that such plans were only partially effective (Ballester et al., 2023). This suggests the need to further develop HHAPs, but also to evaluate the effectiveness of existing plans and revise them accordingly.

Alongside HHAPs, actions to protect human health and well-being from high temperatures may be considered under other mechanisms and policies. For example, ‘heatwaves and drought’ are the health threats most frequently covered by national climate adaptation policies and national health strategies according to the European Climate and Health Observatory (2022a). In addition, greater focus on preventing and responding to high temperatures in occupational health and safety legislation (EU-OSHA, 2023) as well as spatial planning and building design regulations can help protect the population from heat.

Conclusions and opportunities for action

Establishment of surveillance systems for heat impacts on health

Despite the increasing duration, frequency, and magnitude of high temperature events in Europe and stark warnings about future health risks from heat under climate change (EEA, 2024a), the coverage of systems to monitor the health impacts of heat is far from complete. In countries without surveillance systems, information on the number of deaths associated with heat may be missing, whereas even in countries with such systems in place, data on heat-related emergency room visits and hospital admissions are rarely collected. This means that both practitioners and decision-makers in Europe may have a limited understanding both of the magnitude of heat impacts on health and the distribution of impacts over time and space (Pascal et al, 2024). Having a spatially nuanced and timely monitoring system that breaks down data demographically would help in the development or redesign of measures and policies to protect people, especially those who are most vulnerable, from heat. Such surveillance systems should be designed around carefully selected thresholds for activation that reflect the level of risk and balance the timely deployment of emergency measures with resource efficiency.

The absence of national or sub-national information about the scale of the impact of heat on human health may also affect the priority given to climate adaptation actions aimed at improved thermal comfort (such as urban greening) and reduce associated resource allocations, which may ultimately affect the development and implementation of climate adaptation policy. Moreover, the lack of baseline information about the health impacts of heat presents a challenge for assessing the effectiveness of planned and implemented responses. Knowing which measures work is crucial for maximising the protection of human health and well-being, as well as ensuring the most efficient use of public funds towards such measures.

Finally, the danger to human health posed by high temperatures outside of monitoring periods highlights the importance of raising awareness about heat-health risks among the general population and implementing longer-term adaptive measures to reduce people’s exposure to high temperatures during the entire warm season.

Further development of HHAPs, with a focus on vulnerable groups

Given the increasing frequency of extreme heat events and the current absence of HHAPs in at least 10 EEA-38 countries, the further development and implementation of HHAPs at national, regional, and local levels is a priority. In fact, all EEA-38 countries signed the Declaration of the Seventh Ministerial Conference on Environment and Health (‘The Budapest Declaration’), where they committed to ‘developing and updating heat-health action plans, to effectively prevent, prepare for and respond to heat-related health risks, while adapting urban planning to address the impacts of urban heat island effects, taking into account the competencies of different levels of governance’ (WHO Europe, 2023).

WHO Europe’s guidance on heat-health action planning (WHO Europe, 2008) identifies eight elements for the successful implementation of a HHAP, namely:

1. agreement on a lead body;
2. accurate and timely alert systems;
3. a heat-related health information plan;
4. a reduction in indoor heat exposure;
5. particular care for vulnerable population groups (see Box 2);
6. preparedness of the health and social care system;
7. long-term urban planning;
8. real-time surveillance and evaluation.

Revised WHO Europe guidance on heat-health action planning is expected in late 2025. This guidance will support authorities developing or revising HHAPs.

Knowledge exchange

The variety of approaches used to forecast, monitor or retrospectively evaluate the impacts of heat creates an opportunity for cross-national learning and collaboration. Likewise, the varying extent of HHAP implementation across Europe offers an opportunity for experience sharing. Multiple actors could support knowledge development and exchange among institutions responsible for managing heat risks to health. For example, in its roadmap for action on health and climate change, IANPHI (2021) commits to enhancing capacity, competence and training through peer-to-peer support and knowledge sharing between NPHIs. The WHO Europe Working Group on Health in Climate Change (HIC) facilitates dialogue and cooperation among the countries in the WHO European Region and the Bonn School on Environment and Health is an avenue for raising awareness and building capacity among public health professionals. Furthermore, the European Climate and Health Observatory — a partnership that brings different stakeholders on climate and health together — strives for public authorities having a greater capacity to anticipate and prevent climate-related threats to health. Observatory partners have committed to support the development of a range of mechanisms to this end, such as public surveillance, forecasting and early warning systems (European Climate and Health Observatory, 2022b).

Knowledge exchange between researchers analysing heat-related mortality and public health practitioners responsible for monitoring and responding to heat impacts on health could also support efforts to reduce heat-related health impacts in Europe. In particular, such exchange could enable the further development of systems to predict the impacts of high temperatures on human health. For example, the Forecaster.health platform provides one way of predicting temperature-related mortality risks across different European regions. Such research-driven endeavours may offer an entry point for countries without specific heat mortality surveillance to develop preventative actions based on epidemiologically calculated risks.

The lack of information in the public domain on the effectiveness of HHAPs in reducing mortality and morbidity (and, more generally, gaps in knowledge about the effectiveness of climate adaptation measures) calls for a greater focus on evaluating which prevention strategies best address heat impacts on health. Also needed is more ‘implementation science’ to facilitate the uptake of evidence-based practice and research into regular use of HHAPs by policy-makers and practitioners. The ongoing work of the European Commission on the strategic research and innovation agenda (SRIA) to identify the priority topics for climate change and health research for the coming years offers an opportunity to boost the evaluation of measures and their uptake.

Action at the European level

Over time, knowledge exchange could lead to a more harmonised approach to monitoring heat-related health impacts across Europe. For example, the existing pan-European mortality monitoring systems could integrate heat-related mortality data. Eurostat runs voluntary mortality data reporting which incorporates variables on some causes of death. EuroMomo, a European mortality monitoring initiative, aims to detect and measure excess deaths related to seasonal influenza, pandemics and other public health threats. The platform currently collects weekly data from 27 European countries and subnational regions. Linking these datasets with meteorological data or providing a specific entry point for countries to report on heat-related deaths could help establish a common European approach to monitoring mortality impacts from heat. This effort would also benefit from integrating the methodological expertise and experience of the expanding body of scientific knowledge on the topic (e.g. Ballester et al., 2023; Van Daalen et al., 2024; Masselot et al., 2023).

Developing a simple pan-European indicator on heat-related mortality may also support a more harmonised approach to monitoring, alongside serving as an important stepping stone for future national and EU efforts to measure — and help in the prevention of — heat-related health impacts. The forthcoming European climate adaptation plan offers opportunities for establishing indicators and targets for preventative actions in response to increasing temperatures over the next century. Increased coordination at the European level may support the implementation of good practices for heat-health surveillance and the execution of measures that ultimately protect people from the health impacts of heat.