Delhi is in the grip of an intense heatwave this week, with daytime temperatures soaring to 44-46°C in many parts of the NCR. But what makes this summer particularly punishing is how the heat lingers long after the Sun goes down. Meaning, evenings and nights offer little relief, turning homes into ovens and making sleep difficult for millions. On May 19, maximum temperatures hit 45°C across several stations, while minimums stayed elevated around 28°C or higher. Through Tuesday night, temperatures hovered around levels usually experienced during day hours. Read Full Story According to AQI.in, the nighttime temperature at 12 am on May 20 was at 39°C, later dropping to 36°C at around 5 am before climbing back up sharply to 40°C by 9 am on Wednesday morning. An aerial view of a dense cityscape of Delhi as the Sun sets. (Photo: Pexels) HOT DAYS AND HOT NIGHTS TOO Forecasts for May 20–22 show daytime highs of 43–46°C and nighttime lows hovering between 26–29°C, well above normal. In places like Gurgaon and other NCR areas, the temperatures were still hovering near 40°C even as evening approached. We are in this phase now when temperatures are still in the range of 44 to 46°c in most stations of #Delhi NCR even at 5:15pm in the evening. Temperatures can sustain around 40°c even after sunset for an hour or so... Peak #Heatwave begins now, when afternoon are extremly hot and pic.twitter.com/9F9aCrMDAN— Weatherman Navdeep Dahiya (@navdeepdahiya55) May 19, 2026 These hotter nights mean the air barely cools, leaving residents tossing and turning in stuffy rooms, unable to find what is needed the most after a long day spent bearing extremely hot temperatures, which is rest. This pattern matches a worrying longer-term trend that is increasingly emerging across Indian cities. Warm nights in Delhi are becoming more common, with minimum temperatures staying unusually high even in April and May. WHAT'S BEHIND DELHI'S HOT NIGHT? So the question is, why does Delhi stay so hot at night? A big reason is the way our city is built. Concrete roads, brick buildings, asphalt, and dense construction act like giant heat sponges. These dense, heat-absorbing structures soak up the Sun’s constant heat and energy all day and release it slowly after sunset. A view of a dense Delhi neighbourhood. (Photo: Unsplash) This is known as the urban heat island effect, where cities remain several degrees warmer than nearby rural areas—often 1°C to 6°C hotter. With fewer trees and green spaces, especially in crowded neighbourhoods, there is nothing to absorb or block this stored heat. The buildings and roads keep radiating warmth deep into the night, preventing the usual drop in temperature. WHAT'S AHEAD? Over the past decades, very warm nights in India have increased faster than hot days. In Delhi and other cities, emissions from vehicles, air conditioners, and industries add to the heat. Researchers have found that nights are warming quicker, turning what used to be rare events into regular summer features. The extra heat trapped in the atmosphere combines with our urban concrete jungle to keep temperatures high around the clock. Humidity adds to the misery, making it harder for the body to cool down through sweat. People sweat during an ongoing heatwave near Red Fort in New Delhi. (Photo: PTI) And then, there's the human cost. These hot nights are more than uncomfortable. They disrupt sleep, strain the heart, and raise health risks, especially for the elderly, children, outdoor workers, and those without air conditioning. Low-income areas with dense housing and minimal greenery suffer the most. Solutions are actually simple, experts say. We just need greener urban solutions. More trees, more cool roofs, better urban planning, and heat action plans that address nighttime temperatures too. A view of an urban street with trees on both sides. illustarting green urban planning. (Photo: Pexels) Until then, Delhi’s summers are likely to test residents’ limits even after the Sun sets. As this heatwave continues into the week, staying hydrated, avoiding peak heat, and using fans or coolers wisely can help. But the deeper challenge of building a cooler, greener city for the hot nights ahead remains. Ends
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