Why you found heat so oppressive: 52 degree Celsius —‘feel’ temperature on Friday evening in Delhi
DELHI: High humidity and lack of rain made the temperature in Delhi feel like 48 degree Celsius on Friday afternoon and 52 degree Celsius by the evening. The actual high, as measured at the Safdarjung weather station, was 39 degrees Celsius. High humidity, which on Friday ranged between 74% and 49% causes this wet-bulb effect, where the temperatures being felt are higher than they actually are. The day’s maximum temperature of 39 degree Celsius was two degrees above the season’s normal. The minimum temperature on Friday was 29.2 degree Celsius, a notch above the season’s average and around one below Thursday’s 30 degree Celsius. Several areas in the city recorded a maximum temperature of over 40 degree Celsius, with Najafgarh logging 40.5 degree Celsius (actual temperature) for the highest in the city, followed by 40.4 degrees at Pitampura, 40.3 degrees at Pusa and 40.1 degree Celsius at Jafarpur. The city has been receiving moist easterly winds that have raised the humidity levels while partial or weak cloud cover has led to no rainfall and kept the daytime temperatures high. This is the reason the feel temperature, or heat index, has remained high, always spiking as the day progresses. “This occurs during summer when the humidity increases as the day unfolds but the temperature does not show much variation or the maximum they fall is a degree or two between 1pm and 5pm,” explained Mahesh Palawat, vice-chairman, Skymet, a private weather forecasting agency. RK Jenamani, senior weather scientist, India Meteorological Department, reiterated, “The temperatures do feel warmer due to the high humidity. But since we have not developed such a system yet in India to calculate heat index, we can’t comment on the feel temperature or heat index calculated using different systems. We have not validated the methods used to calculate heat index and their consideration of Delhi's weather conditions while doing it.” Experts felt that calculating the heat index was a must for a region like Delhi, where the humidity rises alongside heat and people are unaware of its ill effects. The heat index has a lot of relevance for Delhi because the human body has limited capacity to deal with humidity, said Avikal Somvanshi, senior programme manager, Centre for Science and Environment. Somvanshi went on, “When there is dry heat, the body sweats, which evaporates and cools the body. But during humidity, one sweats but the body cannot cool down because the sweat doesn’t evaporate. Thus, the heat balance of the body goes askew due to high humidity and can result in organ failure. That is the reason most heatstroke deaths in India occur in coastal Andhra Pradesh with its high humidity and temperature and not in Rajasthan with its dry heat.” According to the weather department, Delhi has been deprived of rain for over four days now though IMD had been forecasting rain and issuing rain alerts and then changing its predictions. Amid this uncertainty, respite from heat and humidity is likely from Saturday evening. The maximum and minimum temperature on Saturday may hover between 37 and 29 degree Celsius. “There is a possibility of rain from Saturday evening because winds from the Bay of Bengal and Arabian sea are bringing in moisture and the monsoon line of trough is moving north again from central India. Light to moderate rain may continue till Sunday. There might be isolated intense spells on Sunday,” said Palawat.