Hot nights are worsening India’s heat crisis. But low-tech solutions show some promise.
Across Indian cities, nighttime temperatures are higher than they were 15 years ago, according to a 2024 analysis by the Centre for Science and Environment in Delhi, of which Somvanshi was a contributor. (https://www.cseindia.org/decoding-the-urban-heat-stress-among-indian-cities-12191) For Merina Yasmin and her husband and 5-year-old daughter, who live in a one-room home in an informal settlement on the edge of Delhi, sleepless nights have become all too common in the summer. Her home is made of tin sheets that heat up under the scorching sun all day and remain warm even after sunset. The room doesn’t have windows or a refrigerator, and the only source of relief is a desert cooler — a device with a fan and a water tank that blows cool air by evaporating water. But even that is unreliable because of frequent power cuts. Yasmin said that she looks forward to going to work, because it’s her only escape from the heat. She is a domestic worker for families who have air conditioning. But after washing their dishes and mopping their floors all day, she can’t even catch some rest because of the heat in her own home. “Sometimes, I don’t feel like I am a human being,” she said. Summer is in full swing in India, and many cities are experiencing scorching heat. And in India’s bustling cities, as the sun goes down and the worst of the day’s heat is over, an insidious threat looms: high nighttime temperatures. But some low-tech solutions may help address the problem. Avikal Somvanshi, a researcher who studies heat stress in urban India, said that India has always been hot but this kind of heat is not normal. “Climate change is actually fueling the heat waves,” he said. It’s making them longer and more frequent, he said. This year, heat waves in India began occurring as early as February, and many states are experiencing temperatures above 100 degrees Fahrenheit. Last June, Delhi recorded its hottest night in over 50 years with a low of 95 degrees. Across Indian cities, nighttime temperatures are higher than they were 15 years ago, according to a 2024 analysis by the Centre for Science and Environment in Delhi, of which Somvanshi was a contributor. Cities tend to be hotter than their surrounding rural areas even in the day, because of the way they’re built. The concrete, urban environment traps and radiates heat, and there’s less green cover to offset it. But even greener parts of Delhi are seeing elevated nighttime temperatures. “Having tree cover can help you get shade during the daytime temperature, but it seems to be totally ineffective in cooling down things at night,” Somvanshi said. To make things worse, urban India’s densely packed homes offer little ventilation. “We’re really starting to reach the temperatures and humidity levels that we associate with a potential unlivable situation,” said Caroline Buckee, an epidemiologist at Harvard University who is studying the health effects of extreme heat in India. “Even if the temperature outside comes down, the housing itself absorbs the heat in the day, and then, it doesn’t cool down at night,” Buckee said. “And so, the temperature is remaining essentially constant throughout the day and night.” The situation is especially detrimental for people like Yasmin, one of the millions of women who are part of India’s informal economy. They face grueling temperatures and yet, how it affects their health isn’t fully understood, Buckee said. “Really, there are some glaring gaps when it comes to the physiological impacts of heat on women, on the reproductive health of women, and most importantly, of people who live in places most affected by climate change, where extreme heat is becoming more and more of a problem,” Buckee said. To bridge this data gap, she and her colleagues are conducting a study in the western Indian city of Ahmedabad. They have given Fitbits to hundreds of female workers there to monitor their physical stress.