Extreme heat is no longer just an uncomfortable part of summer—it has become a growing global public health challenge. In 2026, severe heatwaves affected large parts of India, Europe, the United States, and many other regions, contributing to overwhelmed emergency departments and rising mortality. During late June alone, Europe reported more than 10,000 heat-related deaths. As extreme heat events become more frequent and intense, health experts warn that they place increasing strain on the human body, healthcare systems, and communities worldwide.
High temperatures affect nearly every organ system in the body, and serious illness can develop quickly. When temperatures remain elevated for several consecutive days, the body’s ability to cool itself through sweating becomes less effective. This increases the risk of dehydration, heat cramps, heat exhaustion, and heat stroke—a life-threatening medical emergency that can lead to organ failure if not treated promptly. Extreme heat also worsens many existing health conditions by placing additional stress on the cardiovascular system, increasing the risk of heart attacks, strokes, kidney injury, and respiratory complications.
Some groups face significantly higher risks than others. Older adults and young children are particularly vulnerable because their bodies are less efficient at regulating temperature. People living with chronic conditions such as heart disease, lung disease, diabetes, or kidney disease are also at greater risk of heat-related illness. Outdoor workers, athletes, and anyone spending prolonged periods in direct sunlight face an increased likelihood of heat exhaustion and heat stroke, especially during extended heatwaves.
Pregnant women represent another high-risk group. Research has linked prolonged exposure to extreme heat with an increased risk of preterm birth, stillbirth, low birth weight, gestational diabetes, and preeclampsia. These risks can be especially severe in regions such as India, Pakistan, Bangladesh, and parts of Africa, where millions of people lack access to air conditioning, reliable electricity, or housing designed to remain cool during periods of extreme heat. In many communities, indoor temperatures remain dangerously high even overnight, providing little opportunity for the body to recover.
Extreme heat also affects mental health, although this aspect often receives less attention. A recent international study published in Nature Mental Health, which examined more than 2.6 million hospital admissions across Brazil, Canada, Chile, and New Zealand, found that prolonged periods of extreme heat were associated with increased hospital admissions for mental and behavioral disorders, particularly among older adults and individuals with pre-existing mental health conditions. Researchers suggest that high temperatures may contribute to anxiety, irritability, aggression, sleep disruption, difficulty concentrating, and emotional distress, while dehydration can further impair normal brain function.
Healthcare systems also come under significant pressure during prolonged heatwaves. Many hospitals in parts of Africa, South Asia, and other lower-income regions continue to operate without adequate air conditioning because of aging infrastructure, unreliable electricity, or limited financial resources. Although most modern hospitals in countries such as the United States, Canada, and much of Western Europe are equipped with climate-control systems, some older facilities continue to face operational challenges during periods of extreme heat.
Health experts recommend several practical steps to reduce the risk of heat-related illness. Staying well hydrated, limiting outdoor activity during the hottest hours of the day, wearing lightweight clothing, using fans or air conditioning whenever available, and visiting public cooling centers if indoor temperatures become unsafe can all help reduce heat exposure. Checking on older neighbors, relatives, and other vulnerable individuals during heatwaves is also important. Recognizing the early signs of heat exhaustion and heat stroke—and seeking immediate medical attention when symptoms develop—can be lifesaving.
