After a six-day ‘near severe’ air spell, rain brings relief for Delhi

Rain and strong winds in Delhi have helped improve the city's air quality, with the 24-hour average air quality index (AQI) dropping to 312 (very poor) on Monday. The city is also expecting more rain in the coming days, which could further improve air quality. However, the India Meteorological Department (IMD) has warned that the rain may also bring fog to the city. Delhi has experienced high levels of pollution throughout November, with the AQI reaching "severe" or "near-severe" levels for most of the month. The city's maximum temperature on Monday was 22°C, the lowest this month.

Rain and strong winds on Monday and Tuesday helped drive out pollutants that had stubbornly clung on to Delhi’s air for weeks, giving the city its best air quality in several days.

New Delhi, India - Nov. 28, 2023: Clouds seen hovering over the skies on a cold morning at Qutub Minar in New Delhi, India, on Tuesday, November 28, 2023. (Photo by Sanchit Khanna/ Hindustan Times) (Hindustan Times)

The Capital’s 24-hour average air quality index (AQI) improved to 312 (very poor), significantly better than 395 at the same time on Monday, and the lowest since November 19, when the average AQI was 301. This number plunged through the day, dropping into the “poor” category with a reading of 275 by 9pm.

The hourly average AQI, which is a better indicator of air quality in a given moment, fared even better, dropping from 358 at 8am to 141 by 6pm. However, this number inched up again later in the evening, as the effects of the rain and wind began to slowly wear off.

Still, another western disturbance is likely to bring Delhi more rain between Wednesday and Thursday, said officials of the India Meteorological Department (IMD), holding out hope that Delhi’s unusual tryst with relatively clean December air may persist for a few more days.

Delhi received 7.2mm of rain in the 24 hours till 8.30 am on Tuesday and another 0.4mm in the next nine hours. This was the city’s first spell of rain in a fortnight, going back to November 10. This is also Delhi’s wettest November in 13 years, with 17.7mm of precipitation so far, the highest since 26mm in November 2010.

The India Meteorological Department (IMD) said that the western disturbance may also tint the city in fog over the next few days. “A cyclonic circulation is forming over Rajasthan and the wind direction will remain easterly, meaning moisture will keep coming towards Delhi over the next two days, with the possibility of a drizzle late on Wednesday and on Thursday. Delhi should also see shallow to moderate fog over the next two days.” said Kuldeep Srivastava, scientist at IMD.

The improved AQI may help Delhi marginally paper over what has been an especially abrasive November in terms of pollution. The Capital has spent much of the month sheathed in pollution, with the AQI either “severe” or “near-severe” (390 and above) for 17 of the 28 days so far.

Delhi recorded a maximum temperature of 22 degrees Celsius (°C), four degrees below normal and the lowest maximum so far this month. The minimum, however, rose to 14.2°C, four above normal.

The Met department said easterly winds will blow over Delhi over the next couple of days, with the minimum temperature unlikely to dip much in that time.