How Heat Is Reshaping the Workforce

This summer’s 2025 FIFA Club World Cup in Qatar offered a glimpse of sport in a warming world. From Philadelphia to Los Angeles, players trained through punishing heat, reporting dizziness and exhaustion. When it became too much, they slipped into cooling vests, retreated to air-conditioned locker rooms, and recovered under the care of medical teams. Meanwhile, the security guards, food vendors, and cleaners who kept the event running worked through the same heat with no relief. 

What unfolded on and around soccer pitches this summer was not an anomaly; it was a measure of how extreme heat is starting to shape the boundaries of work itself, determining who can work, when, and at what cost. 

That same question—of how societies sustain work in a hotter world—is one that negotiators face at COP30 in Brazil. The climate conference’s official thematic days focus in part on adaptation, health, jobs, and workers. Heat does not have its own day, but it is a part of all of them, because extreme heat is no longer a side effect of climate change. It is one of its defining conditions.

Talks in Brazil will expose a widening divide between countries that can pay to protect workers and those that cannot. At COP30, governments have an opportunity to link heat protection to national climate plans, channel climate finance toward labor safeguards, and integrate worker safety into just transition frameworks, so that the transition to a low-carbon world also protects those most exposed to its heat. But right now, the money doesn’t match the scale of the problem. Adaptation finance rarely covers worker safety in any economy, and the gaps are most severe in the Global South, where heat exposure is rising fastest.

Heat-related mortality in the United States has doubled in the past 25 years, underscoring a growing public health and economic threat. Globally, more than 2.4 billion people work under conditions that expose them to dangerous heat that undermines productivity and jeopardizes their health. The impacts are widespread, hitting the agriculture, construction, manufacturing, and service sectors, but the burden is uneven. Low-income and outdoor workers, particularly in the Global South, face the greatest risks with the fewest protections. In the United States, agricultural workers—many of them migrants—are 35 times more likely to die from occupational heat exposure than workers in other industries, according to the National Institutes of Health.

It’s not for a lack of options. We know how to protect people from extreme heat. Yet those most at risk rarely benefit from protective measures that shield wealthier workers and industries from rising temperatures. The result is a widening divide between those able to adapt and those forced to endure.

A recent joint report from the World Health Organization and the World Meteorological Organization described extreme heat as a “public health crisis” for the global workforce. The Climate Change and Workplace Heat Stress report estimates that nearly 23 million workers experience heat-related illnesses each year, including dehydration, heat stroke, and kidney damage. It also estimates that roughly 19,000 workers die annually from heat-related injuries and illnesses.

The report urges governments to adopt “practical, affordable, and effective” protections that can be implemented quickly and at scale. Some protection will come from technology—the cooling suits used by Formula 1 racecar drivers are one example—but staying safe in extreme heat does not necessarily require specialized gear. Decades of occupational health research show that regular hydration, access to shade, and scheduled rest breaks are often enough to prevent most heat-related illnesses, even in severe conditions.

A new study led by Barrak Alahmad at the Harvard T.H. Chan School of Public Health analyzed workplace injury reports and linked each case to heat conditions. He found that the risk of workplace injury rises sharply as temperatures climb. The paper estimates that about 1.2 percent of approximately 28,000 workplace injuries reported to the U.S. Occupational Safety and Health Administration in 2023 were caused by heat.

Crucially, heat safety standards led to lower injury rates. In states with standards, the risk of injury increased by 9 percent during heatwaves, while in states without protections, the risk spiked by 22 percent. The difference wasn’t the weather; it was whether workers had access to rest, shade, water, and modified schedules. 

Extreme heat is not only a health issue; it is an economic and social justice challenge that exposes the fault lines of a warming world. Every lost workday and heat-related illness erodes household incomes, disrupts supply chains, and weakens economies. As extreme heat intensifies, the limits of adaptation will be tested with profound consequences for global labor practices, governments, employers, and workers. Workplace heat protection rules reduce injuries, prevent lost workdays, and keep productivity up. 

Researchers have long warned that extreme heat poses a growing danger in the workplace. Now, as heatwaves become more frequent and intense, labor laws around the world are struggling to keep pace.

Some governments have begun to act. In the United States, at least four states, including California and Oregon, have adopted heat standards that require employers to provide shade, rest, and water when temperatures exceed certain thresholds. 

In Greece, Italy, and Spain, local authorities halted outdoor work during the hottest hours of the day this past summer, when temperatures surged past 115°F (46°C). Japan now requires employers to take protective steps to prevent heat stroke or face fines, and Singapore mandates hourly monitoring of heat and humidity at large outdoor worksites and adjusts schedules accordingly. A handful of countries—including Spain, France, Brazil, and Qatar—have gone further, establishing national occupational heat stress standards that define when work must stop and what protections employers must offer their workers.

But even where protections are on the books, enforcement is uneven. Many gig workers, day laborers, and informal piece-rate workers lack the bargaining power to request breaks or refuse unsafe conditions. Others cannot afford to stop working, even when the heat is life-threatening.

Even the strongest workplace protections cannot change the biological effects of heat. The human body cools itself primarily through sweating and the evaporation of that sweat. When humidity is high, sweat cannot evaporate, and that cooling system begins to fail. Scientists measure this combined stress using the wet-bulb globe temperature (WBGT), which accounts for air temperature, humidity, solar radiation, and wind to gauge how the body actually experiences heat. A WBGT of 95°F (35°C) is considered the upper limit of human survivability, and even at a WBGT of 90°F (32°C), sustained physical activity can push core body temperatures into dangerous territory, leading to heat stroke, organ failure, and death.

Parts of the Persian Gulf, South Asia, and the U.S. Gulf Coast have already reached conditions in which outdoor work cannot be performed safely, even for short periods. Those conditions are projected to become more frequent and widespread.

A 2022 Nature Communications study projects that even if the world succeeds in limiting global warming to 2°C, the number of dangerously hot days will double across the tropics and increase tenfold in the mid-latitudes by 2050. On a planet about 4.9°F (2.7 °C) warmer—our current end-of-century trajectory—33 times more people would be exposed to life-threatening heat on a regular basis. Under those conditions, Southern Europe and the American South could begin to resemble the Persian Gulf, where outdoor labor is already unsafe for several weeks each year. South Asia, sub-Saharan Africa, and parts of Central and South America could expect up to 250 days a year when it is simply too dangerous to work outdoors at all.

This presents a deeper challenge than simply adding more shade breaks or shifting schedules. There will be days—and eventually seasons in some areas—when the physical limits of heat exposure make outdoor labor impossible. Without strong labor protections embedded in climate plans, whole regions could become unable to support the work their economies rely upon. 

The 2026 FIFA World Cup will take place in regions of North America already shaped by deadly heatwaves. And in 2028, Los Angeles will host the Summer Olympics. As Alahmad notes, a heatwave that coincides with a World Cup final or an Olympic opening ceremony could be “catastrophic.”

In the near term, this means cities and organizers will need to plan for heat the way they plan for security threats, transit disruptions, or emergency medical response. Work schedules, event schedules, shade, cooling infrastructure, and worker protections must adjust to conditions that are no longer exceptional, but expected.

But protecting workers from extreme heat is only the start. Over the longer horizon, climate and labor policy must converge. A just transition means not only reducing emissions, but also redesigning the conditions of work as the planet warms. That includes enforceable heat standards, social protections for workers whose jobs may become seasonal or unsafe, and public investment in the spaces and systems that make life and labor possible in hotter climates. At COP30, delegates will debate emissions targets, adaptation finance, and just transition frameworks. Behind those discussions lies a more immediate question: how to make work viable as the planet continues to warm. Embedding heat adaptations and labor safeguards into climate commitments would not only reduce risk but secure a just transition for the people who grow our food, build our cities, and keep our economies running.