Too hot, too humid: why the sustained heatwave in India and Pakistan is so dangerous

India and Pakistan are enduring an unusually severe heatwave that began in mid-April, with temperatures frequently surpassing 46°C and exceeding seasonal averages by 5–8°C. The prolonged heat has driven record electricity demand as people rely on air conditioning, while drought conditions affect over a million square kilometers across both countries. At least 37 deaths have been reported in India and 10 in Pakistan, though underreporting likely means the toll is higher. The extreme heat is linked to persistent high-pressure systems that suppress cloud formation and reduce cooling rain, trapping hot air near the surface. Drier soils and urban heat islands—where concrete and asphalt retain heat—further intensify the conditions, keeping cities dangerously hot even at night. Cities are particularly vulnerable, as they lack natural cooling mechanisms and lack access to cooling for many residents. Climate change is a major factor behind the heatwave’s severity. Research suggests the April 2026 heatwave was made about three times more likely and 1°C hotter due to global warming, which currently stands at around 1.4°C. At this rate, such extreme heatwaves could occur every five years, but with projected warming of 2.6°C by 2100, they may strike every two to three years and be 2.2°C hotter. Humidity worsens the threat, as high moisture levels reduce the effectiveness of sweating—the body’s primary cooling method. In humid conditions, sweat evaporates less efficiently, making it harder for people to regulate their body temperature. This combination of extreme heat and humidity increases the risk of heatstroke and other heat-related illnesses, particularly for vulnerable populations. The World Weather Attribution group has highlighted that climate change is worsening pre-monsoon heatwaves in South Asia, exposing hundreds of millions to longer and deadlier conditions. Without significant reductions in global emissions, such heatwaves will become more frequent and severe, posing growing challenges to public health and infrastructure.