Delhi recorded a temperature of 43.5°C yesterday, but the real factor driving health risks is what is known as the ‘wet-bulb globe temperature’ — a measure combining heat, humidity, wind speed and solar radiation. British climate experts from the University of Reading have warned that Delhi’s urban infrastructure is exacerbating the crisis, turning the city into a heat island where temperatures can be five to eight degrees higher than surrounding rural areas.
Dr Mark Patterson, lead author of the report, said: “The 43.5°C on a thermometer is dangerous enough, but in a city like Delhi, the built environment stores heat during the day and releases it slowly at night. This means residents get no respite. The physiological stress on the body, especially for outdoor workers, is immense.”
The study used satellite data and climate models to map heat distribution across Delhi. It found that densely built areas, with concrete and asphalt surfaces, retained heat far longer than green spaces. Night-time temperatures in central districts remained above 34°C, compared to 28°C in parks and forested zones.
This is not a short-term anomaly. The Indian Meteorological Department has noted that heatwaves have increased in frequency and intensity over the past decade. March 2025 was the hottest March since records began. April followed suit. Now May is on track to break more records.
The consequences for public health are severe. Heatstroke cases have surged by 40% compared to last year. Hospitals are reporting a rise in cardiovascular and respiratory emergencies. The report emphasises that the most vulnerable are the poor who lack access to air conditioning or even shade.
Solutions exist. The UK experts point to ‘cool roofs’ painted with reflective materials, urban tree cover, and better building insulation. But implementation lags. “The infrastructure deficit is staggering,” said Dr Patterson. “The longer we delay, the more lives are lost.”
The Indian government has invested in early warning systems and opened cooling centres, but coverage is sparse. The real challenge is to redesign the city itself for a hotter future. As global temperatures climb, the lesson from Delhi is clear: heatwaves are no longer just weather events; they are a structural crisis of urban planning.
