Heat Stress & Extreme Heat Events: The Bigger Picture

Heat stress is no longer a seasonal or regional concern—it's a global public health challenge rapidly escalating due to climate change. As average temperatures rise, heatwaves become more frequent and intense, and extreme weather becomes the new normal, the risk of heat-related illness and death is rising for workers, athletes, military personnel, and vulnerable populations everywhere. This blog post explores how climate change is reshaping our understanding of heat stress, who is being affected, and what we can do to prepare.

Rising Temperatures, Rising Risks

According to the Intergovernmental Panel on Climate Change (IPCC), global surface temperatures have risen by more than 1.1°C since pre-industrial times. This increase has had a direct impact on the frequency, intensity, and duration of heatwaves around the world. What used to be rare events are now seasonal threats.

Extreme heat doesn't just bring discomfort—it significantly increases the risk of heat-related illnesses such as heat exhaustion, heat stroke, and dehydration. In the U.S. alone, the Centers for Disease Control and Prevention (CDC) estimates that over 1,300 people die each year from extreme heat, with many more suffering from non-fatal illnesses that impact productivity, well-being, and long-term health.

Vulnerable Populations and Unequal Impact

The health effects of heat stress aren't distributed equally. Certain groups are far more vulnerable to its impacts due to age, occupation, health status, or socioeconomic conditions:

• Outdoor workers in construction, agriculture, and logistics are exposed to extreme heat for long periods, often with limited access to shade or cooling.
• Older adults and children have less effective thermoregulation, making them more susceptible to heat-related illnesses.
• People with chronic conditions such as cardiovascular or respiratory disease face greater health risks during heat events.
• Low-income communities often lack access to air conditioning, green space, or proper insulation, increasing their exposure to indoor heat.

The Urban Heat Island Effect

Cities are particularly vulnerable to heat stress due to the urban heat island (UHI) effect. Asphalt, concrete, and glass absorb and retain heat, raising city temperatures significantly higher than surrounding rural areas, sometimes by 5–10°F or more.

This effect is exacerbated in areas with minimal green infrastructure. An EPA study in 2021 found that neighborhoods with fewer trees, more impervious surfaces, and lower-income residents face disproportionately higher temperatures. As climate change drives global warming, the urban heat island effect becomes more dangerous and widespread.

Impact on Work and Productivity

Heat stress is also an economic issue. A 2022 report from the International Labour Organization (ILO) estimates that heat-related productivity losses could reach 2.2% of total working hours globally by 2030, equivalent to 80 million full-time jobs.

In physically demanding industries, high temperatures reduce the body's ability to work efficiently and safely. Workers may need longer rest breaks, which reduce productivity, or may push themselves too hard, leading to injuries and illness. In either case, the economic impact is significant.

Implications for Agriculture and Food Systems

Agricultural workers are among the hardest hit by rising temperatures. They often labor in direct sun during peak heat hours, perform strenuous physical tasks, and lack sufficient access to cooling infrastructure.

Hot weather affects not only the workers but also the crops they tend. Excessive heat can reduce crop yields, impact livestock health, and alter growing seasons, leading to food insecurity. As global demand for food increases, the stress placed on these workers—and the systems they support—continues to grow.

Heat Stress in Military and Emergency Operations

Military personnel are increasingly encountering heat stress during training and deployment. Exercises in hot and humid conditions pose a dual threat: physically degrading troops and compromised mission readiness.

It also affects emergency responders, who must work long shifts in extreme temperatures during natural disasters such as wildfires, floods, and hurricanes. Without proper heat management strategies and equipment, these professionals face a severe risk of heat-related illnesses in the line of duty.

Sports and Athletics in a Warmer World

Athletes at all levels—from youth leagues to professional competitions—are being pushed to perform in higher temperatures and more unpredictable weather conditions. Training schedules are being shifted, cooling breaks are being added, and events are being canceled due to safety concerns.

Recent studies show that the risk of exertional heat illness increases significantly when WBGT (Wet Bulb Globe Temperature) exceeds 82°F (27.8°C), a threshold reached more frequently across the U.S. and globally. Sports organizations are now reassessing heat safety protocols to reflect these changing conditions.

Monitoring, Mitigation, and Adaptation

Responding to heat stress in increasingly hotter environments requires a multi-layered approach:

Monitoring

• Heat stress meters: Devices that measure WBGT are essential for real-time risk assessments.
• Wearable sensors: Monitoring core temperature, heart rate, and exertion helps identify early signs of heat illness.
• Weather data: Access to localized heat forecasts and heat alerts helps with planning and prevention.

Mitigation

• Urban greening: Planting trees, creating green roofs, and investing in parks can help lower city temperatures.
• Reflective materials: Cool roofing and pavement coatings reduce heat absorption.
• Energy efficiency: Better building insulation and climate-smart design reduce indoor heat buildup.

Adaptation

• Work-rest schedules: Guidelines from OSHA, NIOSH, and DoD provide frameworks for safe activity in hot environments.
• Hydration strategies: Ensuring access to water and electrolyte solutions is critical.
• Cooling infrastructure: Shade structures, misting stations, and air-conditioned recovery zones provide safe relief during heat events.

Climate Policy and Heat Health

Governments and regulatory bodies are beginning to respond to the rising heat threat. In the U.S., OSHA's National Emphasis Program on heat-related hazards increases enforcement and education on job sites. Several states, including California, Oregon, and Washington, have adopted specific heat safety standards.

Internationally, countries like India and Australia, as well as members of the European Union, are investing in early warning systems, heat action plans, and climate-resilient infrastructure. The World Health Organization (WHO) and the UN Framework Convention on Climate Change (UNFCCC) also integrate heat health into broader climate resilience strategies.

The Bigger Picture

Heat stress is not just a weather-related health hazard—it's a systemic challenge that intersects with climate change, labor rights, public safety, and urban planning. Left unaddressed, the human and economic costs will only grow.

But with targeted investment in technology, infrastructure, training, and policy reform, we can adapt to a hotter world. By viewing heat stress through the lens of climate resilience, we can build safer workplaces, healthier communities, and a more sustainable future for everyone.