When the mercury hit 43.5C in Delhi this week, social media lit up with comparisons to Britain’s own heatwave records. But as UK weather experts were quick to explain, the numbers tell only half the story. The real culprit, they say, is something far less headline-grabbing but far more punishing: humidity.
Dr. Hannah Cloke, a professor of hydrology at the University of Reading, put it bluntly: “Heat is not just about temperature. It’s about the body’s ability to cool itself through sweat. In dry heat, that works. In humid heat, it fails.” And Delhi, with its monsoon season looming, is nothing but humid.
The British heatwave of 2022 saw temperatures soar to 40.3C in Coningsby, Lincolnshire. It was unprecedented, dangerous, and for many, unbearable. But even at that peak, the air was dry. The so-called “wet-bulb globe temperature” – a measure that combines heat, humidity, and wind – remained within survivable limits. In Delhi, that number is dangerously higher.
What does this feel like on the ground? For those of us who have sweltered through a British heatwave with a fan and a cold flannel, it’s hard to imagine. But imagine stepping outside into a sauna that is also a furnace. Your breath catches. Your skin prickles with moisture that never evaporates. The heat is not just on you; it is in you.
The cultural shift, as ever, is telling. In Britain, we complain. We buy paddling pools and fans. We cancel trains. In Delhi, people adapt. They cover their heads, drink salted lassi, and wait for the monsoon. But adaptation has limits. The human cost is measured in hospital admissions, in lost working hours, in lives cut short.
Climate change, of course, is the backdrop. As global temperatures rise, so does the air’s capacity to hold moisture. The UK, too, is seeing more humid heatwaves. Last year’s record-breaking spell in London came with warnings about “tropical nights” where temperatures stay above 20C. It is a taste of what is to come for many temperate regions.
For now, though, the difference remains stark. The British heatwave is a crisis of infrastructure, of preparedness. Delhi’s is a crisis of survival. Both are part of the same story: a world getting hotter, in ways our bodies were not designed to handle.
As one weather expert put it: “The numbers don’t reflect the suffering.” And that, perhaps, is the most important lesson of all.
