Extreme heat is no longer a distant environmental concern; it has become one of the most urgent threats to human health, work, and economies worldwide. According to new reports from the United Nations and the International Labour Organization (ILO), heat stress—defined as exposure to temperatures beyond the body’s ability to cope—has reached alarming levels, driven by climate change and more frequent, intense heatwaves. From agriculture fields in South Asia to construction sites in Africa, millions of workers are on the frontline of a crisis that is reshaping the world of work.
Heat Stress Defined
The ILO defines heat stress as conditions where the temperature exceeds what the human body can tolerate without suffering physical or psychological harm. This usually occurs at temperatures above 35°C in humid climates, where heat can overwhelm the body’s cooling mechanisms. At this point, work becomes not only physically draining but also dangerous. Prolonged exposure may lead to dehydration, kidney dysfunction, neurological disorders, or in extreme cases, heatstroke—sometimes fatal. “Heat stress is already harming the health and livelihoods of billions of workers, especially in the most vulnerable communities,” said Dr. Jeremy Farrar, WHO Assistant Director-General for Health Promotion. His warning underscores the urgency of recognizing heat stress not merely as a health issue, but also as a profound social and economic challenge.
A Global Challenge
The scale of the problem is staggering. Between 2000 and 2019, extreme heat caused approximately 489,000 deaths annually, according to the World Meteorological Organization (WMO). Nearly half of these occurred in Asia, and more than one-third in Europe. Vulnerable groups—children, older adults, and low-income workers—bear the greatest burden. Moreover, the impacts are not confined to traditionally hot regions. “Occupational heat stress has become a global societal challenge, no longer confined to countries close to the equator, as highlighted by the recent heatwave in Europe,” said Ko Barrett, WMO Deputy Secretary-General. In 2024, global temperatures were recorded at 1.55°C above pre-industrial levels, making it the hottest year ever documented. Daytime highs above 40°C became commonplace, with some areas surpassing 50°C.
The Productivity Loss
Beyond health, extreme heat is silently eroding global productivity. The ILO’s 2019 report projected that by 2030, 2.2% of total working hours worldwide will be lost each year due to rising temperatures. This loss equals 80 million full-time jobs, representing a massive economic blow valued at $2.4 trillion annually. The hardest-hit sector will be agriculture, which employs 940 million people globally. It is expected to account for 60% of lost working hours by 2030, as laborers exposed to outdoor heat struggle to cope with intensifying conditions. Construction, another highly vulnerable sector, is projected to account for nearly 19% of lost hours. Other industries at risk include environmental services, waste collection, emergency response, transport, tourism, sports, and heavy manufacturing. The economic consequences extend beyond lost hours. Reduced productivity limits income, worsens poverty, and deepens inequality, especially in low- and middle-income countries. “Protection of workers from extreme heat is not just a health imperative but an economic necessity,” emphasized Barrett of WMO.
Regional Inequalities
The burden of heat stress will not be evenly distributed. South Asia and West Africa are projected to lose about 5% of total working hours by 2030, equivalent to 43 million and 9 million jobs respectively. These regions are also home to some of the world’s poorest populations, who have fewer resources to adapt to extreme heat. Women and men are affected differently. Millions of women engaged in subsistence farming face rising risks to health and livelihoods, while men dominate construction—a sector highly exposed to outdoor heat. As poverty worsens, families dependent on these jobs may face further insecurity, forcing migration from rural areas to urban centers or across borders in search of safer livelihoods. The ILO warns that such patterns will exacerbate existing inequalities, including the prevalence of informal, insecure work and the lack of social protection in low-income countries.
Asia: Warming Twice as Fast
Recent findings show Asia is warming twice as fast as the global average, intensifying climate extremes. In 2024, China broke monthly temperature records repeatedly, while droughts affected over 4.76 million people and damaged hundreds of thousands of hectares of crops. Simultaneously, severe floods in Kazakhstan, caused by record rainfall and glacier melt, became the worst in 70 years. Nepal, though better prepared with early warning systems, still experienced deadly landslides and floods, killing over 246 people. “This is the first time in 65 years that flooding was this bad. We had zero casualties thanks to preparedness and rescue measures, but the damage was extensive,” said Ramesh Karki, Mayor of Barahakshetra in Nepal, pointing to the importance of resilience and early action.
Cities on the Frontline
Urban areas are particularly vulnerable due to the “urban heat island effect,” where dense city landscapes trap heat, raising temperatures well above those in surrounding rural areas. According to WMO, the health impacts of heat are especially severe in cities, where air pollution and poor housing conditions magnify risks. In July 2025, Sweden and Finland experienced unusually prolonged heatwaves, while Türkiye recorded a new national high of 50.5°C. Across Asia and North Africa, many countries faced daily highs above 45°C. The combination of extreme heat, wildfires, and poor air quality has created cascading crises—from disrupted power and water supplies in Iraq and Iran to mass evacuations in Greece, Cyprus, and the United States. In Canada, one of the worst wildfire seasons on record burned 6.6 million hectares, with smoke traveling across the Atlantic to darken skies over Europe.
Human Cost and Social Impacts
The toll of heat stress is not only measured in lost jobs or economic figures but also in lives and livelihoods. The World Health Organization estimates that climate change will cause an additional 250,000 deaths annually between 2030 and 2050 due to malnutrition, malaria, diarrhea, and heat stress. A study published in The Lancet highlighted the labor consequences: in 2021 alone, heat exposure resulted in the loss of 470 billion potential working hours globally, disproportionately affecting low- and middle-income countries. This has compounded the cost-of-living crisis, reducing incomes where they are needed most. The social consequences are equally severe. As rural workers abandon agriculture for urban opportunities, migration flows increase, straining already fragile infrastructure. Heat stress also raises risks for pregnant women, children, and elderly populations, aggravating health inequalities.
Path Forward
Despite the daunting figures, experts stress that solutions exist. The WHO and WMO have called for urgent occupational heat action plans tailored to industries and regions. Their recommendations include: developing targeted occupational heat-health policies based on local vulnerabilities; training health professionals, employers, and workers to recognize and treat heat stress, which is often misdiagnosed; prioritizing protections for middle-aged and older workers, and those with chronic conditions; strengthening early warning systems, particularly in vulnerable regions; and promoting affordable, scalable innovations such as cooling shelters, protective clothing, and improved workplace design. Scaling up heat-health warning systems in just 57 countries could save nearly 100,000 lives annually, according to WHO and WMO.
A Call to Action
“This report represents a critical milestone in our collective response to the growing threat of extreme heat in the world of work,” said Joaquim Pintado Nunes, ILO Chief of Occupational Safety and Health. The guidance, he added, aligns with the ILO’s mission to ensure safe and healthy working environments as a fundamental right. Joy Shumake-Guillemot, lead of the WHO-WMO Climate and Health Joint Programme, went further: “This is not just a climate issue; it’s a public health emergency.” With global warming showing no signs of slowing, coordinated international action is essential. Protecting workers from heat is not only about saving lives but also about safeguarding economies and ensuring decent work for future generations.