What was Delhi air quality on Deepavali night?Even reading yesterday’s Diwali AQI will discomfort your lungs; check data

A thick grey haze engulfed Delhi on Monday morning, reducing visibility and causing respiratory distress to residents as the city’s Air Quality Index (AQI) dropped to 370, in the ‘very poor’ category.

The severe deterioration followed a night of widespread firecracker bursting during Diwali celebrations, well beyond the limited hours permitted by the Supreme Court.

According to the Swiss monitoring platform IQAir, Delhi ranked as the third-most polluted city in the world on Monday morning.

‘Severe’ air quality across monitoring stations

The Central Pollution Control Board (CPCB) classified the citywide average AQI as ‘very poor’, with numerous monitoring stations already recording ‘severe’ levels above 400.

The worst-affected areas included Sonia Vihar, which recorded an AQI of 463 on Diwali night, alongside Jahangirpuri at 450. By Monday morning, DTU and Burari Crossing both recorded an AQI of 437.

The air quality is expected to deteriorate further, entering the ‘severe’ category during the day.

PM2.5 concentrations breach WHO limits

According to a Reuters report, the concentration of hazardous pollutants spiked drastically overnight.

IQAir data revealed PM2.5 concentrations reached 170 micrograms per cubic metre (µg/m³)—roughly 34 times the World Health Organisation’s annual guideline value. Other significant pollutant readings included PM10 at 126 µg/m³ and carbon monoxide at 1,461.5 µg/m³.

Independent monitoring platform AQI.in reported a staggering peak AQI of 2,283 immediately after Diwali, then settled to a “hazardous” 637 by Monday morning.

Navdeep Dahiya, a senior PM Meteorologist at Zomato, said peak AQI levels above 1,000 were observed in New Delhi between 11:30 pm and 6:30am.

“Easterly winds at work. Now, at 11:30 am, AQI has improved drastically, now at 286 vs 379 yesterday at the same time (pre-Diwali celebrations),” he wrote.

Dahiya also expects the smog to completely disperse and the AQI to improve by the evening.

Unfavourable weather traps pollutants

The Air Quality Early Warning System attributed the rapid decline to a combination of Diwali emissions, regional stubble burning, and highly unfavourable meteorological conditions.

A ventilation index below 6,000 square metres per second and an average wind speed under 10 kmph severely restricted the dispersion of accumulated smoke.

The agency forecast that the overall city AQI is likely to slip fully into the ‘severe’ category during the day and remain there for the subsequent few days.

Court restrictions flouted amid winter crisis

The post-Diwali pollution spike exacerbated an ongoing air quality crisis in Delhi, an annual winter challenge caused by cold, heavy air trapping vehicular emissions and construction dust.

Delhi has battled poor air quality for over a week, prompting authorities to invoke restrictions under the graded action plan on Friday, including shifting schools to online classes.

Despite the Supreme Court mandating the use of only certified low-polluting firecrackers during restricted hours, residents across Delhi—and the financial capital, Mumbai—reported fireworks continuing late into the night, leaving iconic landmarks like India Gate shrouded in heavy smog.