When the hot weather hits, will you and your community be ready? For far too many people around the world, the answer is no, and the consequences will be deadly. 

Global temperatures are projected to reach unprecedented levels again this year, and the consequences of inaction will be dire and widespread. As part of our #HeatReady campaign, the Global Heat Health Information Network urges governments, organizations, and individuals worldwide to take immediate action to prepare for the 2024 heat season, which is already off to a record start. Source 2023 was the world’s warmest year on record, by far | NOAA  

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Heat is a silent killer, expect major health impacts in 2024.

The data is clear: heat kills, and heatwaves are becoming more frequent, intense, and prolonged due to climate change. Source AR6 Synthesis Report: Climate Change 2023 (IPCC)    

2023 was the warmest year on record by a significant margin. It highlighted the devastating impacts of extreme heat, with countries around the globe experiencing record-breaking temperatures.

Europe saw unprecedented heat, leading to thousands of heat-related deaths, Source Analyses of heat related mortality from 2023 are not yet available, but a recent study found that 61,672 excess deaths occurred in Europe due to heat in the summer of 2022. overwhelmed healthcare systems, Source Parisians are most at risk of dying in European heatwaves   and wildfires from Greece to Spain. In Asia, countries including India and Pakistan endured another searing heat season, causing significant mortality, reducing agricultural productivity, and exacerbating water shortages. The United States (US) faced similar challenges, with cities like Phoenix and Las Vegas recording their highest temperatures on record, straining public health infrastructure and leading to numerous fatalities.
 
These trends are projected to continue into 2024. According to the World Meteorological Organization, this year is already shaping up to be one of the hottest on record, driven by continuing climate trends and the influence of El Niño – a recurring climate pattern. There’s a one-in-three chance that 2024 will be warmer than 2023, and a 99% chance that 2024 will rank among the top five warmest years recorded. Source 2023 was the world’s warmest year on record, by far | NOAA  As extreme temperatures have soared and persisted since May across the Sahel, Asia and the Middle East thousands of lives have already been lost to heat in 2024.

Preparation and early warnings are key to saving lives. 

Almost all deaths directly due to excess heat can be prevented. Governments, authorities and relevant public and private organizations from the local to global levels need to act now. 

Alongside stepping up crucial climate change mitigation efforts, immediate adaptation strategies are necessary to protect the millions of people exposed to extreme heat in the short term. These adaptation efforts must be effective, evidence-based, and sustainable, so that we are not simply coping today by making the problem worse in the long term.

Cities, states, and countries should prioritize heat preparedness and response strategies. This includes developing and implementing comprehensive intersectoral Heat Action Plans and Early Warning Systems, enhancing public awareness campaigns, and investing in heat-resilient policies and infrastructure. These interventions should be stress tested to be ready to contend with plausible but unprecedented heat conditions, including other risks such as fire that high temperatures can trigger.

Local authorities should target resources and interventions towards protecting the most vulnerable people in their communities, for example by establishing cool spaces, housing the unhoused, improving quality of housing and cooling for those with thermally unsafe homes, workplaces, and schools, distributing heat health advisories, and ensuring that emergency services are equipped to respond to heat-related illnesses. Administrative actions to reduce exposure to extreme heat, such as ensuring water and power access, modifying working hours, school closures, and dress codes, and civil protection readiness can also be implemented to reduce risk. 

Long-term adaptation strategies implemented now can save lives in the future. Urban planning and design should incorporate and enhance green spaces, utilize reflective materials, and reduce waste heat from vehicles and buildings to mitigate urban heat island effects. Policies should incentivize retrofitting buildings to improve insulation and ventilation, reducing indoor temperatures. Access to safe water supplies for drinking and dousing, as well as sustainable and affordable cooling solutions such as air conditioning and fans, should be expanded, particularly for low-income and vulnerable communities.

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Indirect impacts and compounding risk must be addressed

Governments must also address the indirect and compounding impacts of heat on health. High temperatures can increase and amplify the risks of drought and water shortages, flash floods, wildfires, air pollution, infectious diseases, and UV radiation. 

Heat also impacts labour productivity, mental health, disease transmission, health service delivery, critical infrastructure, congestion in hospitals and public transit, car accidents, agricultural productivity, animal deaths, and outdoor activities. 

Managing these risks requires action from all of society, including comprehensive preparedness and multi-hazard risk management across various sectors, in both the public and private spheres.

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Individuals and community partners have a crucial role to play

While government action is essential, individual preparedness is equally critical. Everyone should know the signs and symptoms of heat illness, and have a personal plan in place to stay safe and protect those in their care before the heat hits. 

It’s crucial to remember that anyone can be impacted by heat, but vulnerable people are hit first and hardest. People who are at increased risk, including the elderly, those with preexisting conditions or on certain medications, workers, young children, and the poor, unhoused or poorly housed are often impacted well before risks become visible for less vulnerable members of the population. 

For those without adequate cooling, indoors can be hotter than outdoors –  and excess indoor heat is deadly. High nighttime temperatures can also be extremely dangerous – even if it’s less hot than during the day – for those who don’t have adequate cooling at home. Humidity and other factors can compound risk even after the sun goes down. 

Simple actions, such as staying hydrated, applying water to the skin, avoiding strenuous activities during peak heat, and checking on elderly neighbours and family members, can save lives. Revisiting traditional knowledge and tips (including diet, working hours, and clothing) can help people cope with extreme heat, particularly in regions historically exposed to significant heat.

Direct impacts of heat on human health are not just characterised by temperature (which is measured in the shade), but by humidity, sun exposure, and wind. Elevated levels of physical activity and clothing also aggravate heat health risk even in cooler conditions.

Across society, there are many opportunities for action that people can take in their daily lives to protect others. For example:

• Employers should ensure safe working conditions for outdoor and heat-exposed workers, providing adequate hydration, breaks, and well-ventilated and shaded recovery areas. 

• Schools, childcare centres and other care providers must have heat response plans to protect children and other vulnerable groups.

• In sports, policies are available in many countries that should be promoted and used to guide safe sport participation during the summer.

• Major international events planned for 2024, including the Paris Olympics could put many thousands more people at risk, as they face extended periods of time outdoors during typically hot periods of the year. Adequate planning by event organizers to keep participants and spectators safe at all mass gatherings is key to saving lives.  

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The time for complacency is over. The 2024 heat season is set to challenge our resilience like never before, but by taking urgent and coordinated action we can save lives. Let us act decisively, with the urgency and commitment that this crisis demands, to protect those most at risk from the avoidable health impacts of heat. 

Joy Shumake-Guillemot
Global Heat Health Information Network 

Lead, WMO-WHO Joint Office for Climate and Health

Sébastien Denys

Chair, IANPHI Climate Change and Health Committee

Ollie Jay

Director, Heat and Health Research Incubator

University of Sydney

Ladd Keith

Associate Professor of Planning
University of Arizona

Rupa Kumar Kolli

Immediate Past President

Indian Meteorological Society

Kris Ebi

Center for Health and the Global Environment University of Washington

Jason Lee

Director, Heat Resilience and Performance Centre

National University of Singapore

Andreas Matzarakis

University of Freiburg, Germany and Democritus University of Thrace, Greece

John Nairn CF

Churchill Fellow (heatwaves)

Australian Bureau of Meteorology and WMO-WHO Joint Office for Climate and Health (retired)

Mathilde Pascal

Climate Change and Health Project Manager

Santé publique France