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As large parts of India and Pakistan continue to endure weeks of relentless heat, climate scientists are warning that the danger goes far beyond uncomfortable summer temperatures. What makes the ongoing heatwave particularly alarming is not just how hot it is, but how long it has lasted and how humidity is making the heat far more dangerous for human health.
Across several regions, temperatures have crossed 46°C, with some locations recording readings 5°C to 8°C above normal seasonal averages. The prolonged heat has strained electricity supplies, worsened drought conditions and increased health risks for millions of people. Scientists say the event offers a glimpse into a future where extreme heat and humidity become increasingly common due to climate change.
Why This Heatwave Is Different
India and Pakistan are no strangers to hot summers. The period before the arrival of the southwest monsoon is traditionally the hottest time of the year. However, researchers say the current heatwave stands out because of its intensity and duration.
One of the key reasons is the presence of persistent high-pressure weather systems over parts of South Asia. These systems act like giant atmospheric lids, trapping hot air close to the ground. They also suppress cloud formation and reduce the chances of rainfall that would otherwise cool the land. As the heat remains locked in place for days or weeks, temperatures continue to rise.
The lack of rain creates another problem. Dry soil absorbs and releases heat differently than moist soil. When the ground is dry, less energy is used to evaporate moisture and more energy goes directly into heating the surface. This creates a feedback loop that intensifies heatwave conditions.
The Hidden Threat of Humidity
Temperature alone does not determine how dangerous a heatwave becomes. Humidity plays a crucial role in how the human body responds to heat. Under normal conditions, the body cools itself through sweating. As sweat evaporates from the skin, it removes heat from the body.
However, when the air already contains large amounts of moisture, sweat evaporates much more slowly. The body keeps producing sweat but receives less cooling in return. As a result, internal body temperature can continue rising even when a person is sweating heavily. This is why experts are increasingly concerned about what are known as humid heatwaves. The combination of high temperature and high humidity can become far more dangerous than either factor on its own.
Research published earlier this year found that rising coastal sea surface temperatures are contributing significantly to the increase in large-scale humid heatwaves around the world. Scientists estimate that warming coastal waters account for 50% to 64% of the observed increase in these events. This finding is especially relevant for South Asia, where many densely populated regions are located near coastlines and are already vulnerable to both extreme heat and high humidity.
Understanding Wet-Bulb Temperature
A term increasingly appearing in discussions about extreme heat is wet-bulb temperature. Wet-bulb temperature is not simply the air temperature. Instead, it measures how effectively the human body can cool itself through sweating. The higher the humidity, the higher the wet-bulb temperature becomes.
For many years, scientists believed that a wet-bulb temperature of 35°C represented the upper limit of human survival. More recent research suggests dangerous conditions can occur at lower thresholds depending on age, health and exposure. Researchers note that for older adults, conditions of 35°C with 90% humidity can be just as dangerous as 45°C with 30% humidity. Even healthy young adults can face serious risks when temperatures reach 45°C alongside moderate humidity levels.
Cities Are Becoming Heat Traps
Urban areas face unique challenges during extreme heat events. Concrete roads, asphalt surfaces and densely packed buildings absorb large amounts of heat during the day and slowly release it throughout the night. This phenomenon, known as the urban heat island effect, prevents cities from cooling down after sunset.
Scientists recently projected that many tropical and subtropical cities could warm faster than expected under future climate scenarios, particularly in monsoon regions such as India. This means that urban populations may experience even more intense heat than surrounding rural areas. Nighttime temperatures are especially important because the human body relies on cooler nights to recover from daytime heat. When nights remain hot, the risk of heat-related illness increases significantly.
Climate Change Is Making Heatwaves Worse
While weather patterns influence individual heatwaves, scientists say climate change is increasing both their likelihood and intensity. According to an analysis by World Weather Attribution, the heatwave that affected parts of India and Pakistan between April 15 and April 29 was made about three times more likely by human-caused climate change. The study also found that the event was approximately 1°C hotter than it would have been in a world without current levels of global warming.
The planet has already warmed by approximately 1.4°C above pre-industrial levels. Scientists warn that if global warming reaches around 2.6°C by the end of the century, heatwaves similar to the current one could occur every two to three years and become even hotter. A recent United Nations-backed climate outlook further warned that the world is highly likely to experience new record-breaking years of heat before 2030.
Not Everyone Faces the Same Risk
Extreme heat does not affect everyone equally. People with access to air conditioning, reliable electricity and insulated housing have more options to protect themselves. For millions of others, especially those working outdoors, escaping the heat is not possible. Construction workers, delivery personnel, farmers, street vendors and daily wage labourers often spend long hours exposed to direct sunlight. Informal settlements frequently lack cooling infrastructure, adequate water supply and reliable electricity. Rural communities may face additional challenges due to limited healthcare access.
Doctors across India have reported rising cases of dehydration, heat exhaustion and heatstroke as temperatures continue to climb. Children, older adults and individuals with existing medical conditions remain among the most vulnerable groups.
Waiting for the Monsoon
For much of South Asia, relief traditionally arrives with the monsoon. Cloud cover and widespread rainfall help lower daytime temperatures, although humidity often remains high. Southern parts of India typically begin receiving monsoon rains in early June, while the system gradually advances across the country over the following weeks. Pakistan generally receives monsoon conditions later, often in July.
Yet scientists caution that the arrival of the monsoon does not eliminate the broader challenge. As climate change continues to warm the atmosphere, extreme heat and dangerous humidity are expected to become more frequent and more severe across the region.
The current heatwave is therefore more than a seasonal weather event. It is a warning about how rising global temperatures are reshaping daily life for hundreds of millions of people. Understanding the combined dangers of heat, humidity and climate change will be critical as South Asia prepares for a hotter future.
References:
https://phys.org/news/2026-05-hot-humid-sustained-india-pakistan.html
https://phys.org/news/2026-03-coastal-emerge-primary-driver-large.html
Sleepless Nights in India: Climate Change leading to hotter nights in many cities
From 45°C Heat to Flood Alerts: India Faces a Dangerous New Era of Climate Extremes
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