Understanding heat risk
Tackling the threat of extreme heat
Extreme heat arises when sustained high temperatures exceed levels that people, natural and built environments, and systems can safely and functionally tolerate. Human decisions and actions, coupled with accelerating climate change, are driving global temperatures upwards, with conditions of greater exposure and vulnerability a reality and worsening. Extreme heat risk is already threatening the health, well-being and functioning of societies and ecosystems.
This has prompted the United Nations Secretary-General to identify extreme heat as a priority climate challenge, calling for urgent, coordinated action through stronger international cooperation and engagement across all levels of society. Addressing extreme heat requires action by governments, communities, civil society, the private sector, scientific and technical institutions, international organizations, and funders and investors. Significant efforts are already underway to strengthen heat knowledge and analytics, improve governance and action, and mobilise heat risk-informed public and private investment in resilience.
What are the impacts of extreme heat?
Impacts span human health, productivity, agricultural systems, technology and the built environment, among others. Both short-term extreme heat events (such as heatwaves) and longer-term exposure to persistent high temperatures pose serious risks. While heatwaves often attract public attention, continuous heat exposure, especially when combined with high humidity, can be equally dangerous and disruptive. Many heat-related illnesses and deaths occur outside officially declared heatwave periods.
Agriculture
Higher temperatures can reduce crop yields, increase water demand and affect livestock health, posing growing challenges for agricultural production and food systems.
Coastal impacts
Marine heatwaves and rising temperatures are affecting coastal ecosystems and fisheries, with implications for communities and economies that depend on them.
Economic impacts
Extreme heat disrupts economies. This page brings together evidence and analysis on the direct and indirect economic costs of heat and approaches to quantify and reduce losses.
Education
Extreme heat disrupts learning outcomes, school attendance, and the safety of students and staff.
Energy and grids
Rising temperatures increase electricity demand for cooling while reducing the efficiency of energy generation, transmission and distribution systems.
Energy-water nexus
Extreme heat exposes the deep structural interdependence between water and energy systems.
Labour
Workers in outdoor and high-exposure occupations face elevated risks from heat stress, highlighting the importance of workplace protections.
Public health
Extreme heat presents a growing public health risk, contributing to illness, excess mortality and pressure on health services.
Transportation
Heat can affect the performance and safety of transport infrastructure, including roads, railways and aviation systems, leading to service disruptions and maintenance challenges.
Urban heat
Dense built environments trap and amplify heat, increasing exposure for urban populations and placing pressure on infrastructure, services and public spaces.
Environmental impacts
Contemporary discussions on climate change and extreme heat remain largely anthropocentric while obscuring broader environmental impacts.
Enlarge image >
Video resources
But there's a powerful, natural solution: green spaces.
Extreme heat risk trends
Modelled estimates show that between 2000 and 2019, approximately 489,000 heat-related deaths occurred each year, with 45 per cent of these in Asia and 36 per cent in Europe.
Almost half the world’s population (3.79 billion) will be living with extreme heat by 2050 if the world reaches 2.0°C of global warming above pre-industrial levels
Extreme heat is a powerful risk multiplier that has profound effects of agrifood systems globally and currently threatens the livelihoods of 1.23 billion people.
Resources on how heat risk evolves
View content on measuring heat and losses, risk trends, attribution studies and compound events.
Measuring risk and losses
This section is intended as a curated compilation of knowledge available through PreventionWeb, not as a definitive source. Work on measuring heat risk and losses continues to evolve through ongoing efforts by partners and the research community. Forward-looking heat risk modelling is an important part of this effort, helping stakeholders estimate potential future losses under different climate scenarios and assess the scale of risk before disasters occur.
Past heatwave events
Examining past events reveals how extreme heat unfolds in different contexts and the consequences when risk is under-anticipated or poorly managed. This section highlights notable events from the 2020s, offering insights into drivers, impacts, responses, and lessons learned.
It is important to note that heatwaves are only one aspect of extreme heat, which also encompasses conditions such as chronic heat and heat stress that can develop more gradually but still pose significant risks.
Additional resources
