Delhi’s AQI likely to turn ‘poor’ from Wednesday: What factors are behind the slip?

File photo

As winter approaches, Delhi’s air quality is expected to worsen from Wednesday, according to the India Meteorological Department (IMD).

The air is likely to remain in the “moderate” category on Monday and Tuesday but is predicted to slip into the “poor” category for six consecutive days starting Wednesday.

“The air quality is very likely to be in the Moderate category from October 13-14. From October 15 onwards, it is expected to be in the Poor category for nearly a week,” the IMD said in its bulletin.

Recent trends and contributing factors

The city’s air quality had improved slightly on Sunday, after nearing the “poor” category on Saturday. The average AQI on Sunday stood at 167 (moderate), down from 199 on Saturday, helped by steady winds blowing at 10–15 kmph.

However, stubble burning has slightly increased, contributing 0.8% to Delhi’s pollution, up from 0.4% the previous day, according to the Centre’s Decision Support System (DSS).

The Ministry of Earth Sciences’ Early Warning System also expects air quality to stay moderate for October 13–14 and turn poor from October 15, remaining so for almost a week.

According to the Central Pollution Control Board (CPCB), Delhi last recorded “poor” air on June 11, with an AQI of 245. Since then, the city has seen 123 days of cleaner air, including 77 days in the “satisfactory” range and 46 in the “moderate” range.

Why pollution rises in October

Air quality in Delhi usually worsens in October due to a combination of factors: retreating monsoon rains, cooler temperatures, stubble burning in neighbouring states, and festive fireworks.

Slower winds and cooler weather create a “temperature inversion,” trapping pollutants near the ground. Smoke carried by north-westerly winds from Punjab and Haryana further worsens the situation, peaking around early November.

On Sunday, vehicles were the biggest contributors to PM2.5 pollution at 19.8%, followed by emissions from Sonipat (9.2%) and Jhajjar (5.1%), while farm fires remained relatively low this year. Between September 15 and October 11, Punjab reported 116 stubble-burning cases and Haryana 11, compared to 533 and 280 last year.

Delhi recorded a maximum temperature of 31.5°C and a minimum of 19.6°C on Sunday. The IMD forecast clear skies and cool northwesterly winds, with maximum temperatures rising to 34°C by Wednesday.

Environment Minister Manjinder Singh Sirsa highlighted that Delhi has recorded 199 days with AQI below 200 this year, almost double the number in 2016, reflecting “real improvement on the ground."