Delhi Surfaces Hit 64C Despite 43.5C Air Reading

The discrepancy arises because official data and thermal imaging measure different things. The IMD records air temperature under standardised conditions, whereas thermal cameras capture the temperature of physical surfaces. On hot days, roads, concrete, vehicles and other exposed materials can become substantially hotter than the surrounding air, and they radiate that heat back, increasing the load absorbed by the human body. The effect is most pronounced in dense urban areas with little shade or vegetation. The contrast can be stark: at one spot the surface measured 61C, but fell to 39.8C when researchers stepped less than ten feet away beneath a tree. "That's the difference just one tree can make," a Greenpeace researcher observed.

The health consequences are serious. Dr A Fathahudeen, a pulmonologist, explained that the core human body temperature is 37C, and that prolonged exposure to extreme heat can push it higher. "When it exceeds 40C, the body ceases to work normally," he said, citing heat exhaustion, headaches, fatigue and, in severe cases, confusion, seizures and even fatal organ failure. He urged residents to drink water regularly, wear loose, light-coloured clothing and carry umbrellas, and called on authorities to advise labourers against working outdoors between 10:30am and 3pm. For Delhi's poorest, however, such precautions are unaffordable. Street vendors near the Red Fort said they had no choice but to work, and residents of cramped neighbourhoods reported that indoor temperatures hovered around 40C, offering little refuge from the relentless heat.