Delhi Records Its Most Polluted Diwali in Five Years as Smog Grounds Flights

Smog hangs over Connaught Place in New Delhi. (Photo: wili hybrid, Wikimedia Commons, CC BY 2.0)

Delhi has recorded its most polluted Diwali in five years, with thick smog blanketing the national capital for days after the festival and disrupting flights at one of the country's busiest airports. According to Central Pollution Control Board (CPCB) data, the city's average Air Quality Index (AQI) reached 376 on Diwali day, November 8, the highest festival-day reading since 2021.

The figure marks a sharp rise from recent years. Delhi's Diwali-day AQI stood at 345 in 2025, 328 in 2024, 218 in 2023 and 312 in 2022. The last time the festival day was worse was in 2021, when the average reading touched 382. The air did not clear quickly either. On the morning after Diwali, the AQI was still 370 at 9 am, the worst post-Diwali morning reading since 2021, and Swiss monitoring organisation IQAir ranked Delhi the world's third most polluted city that day.

A Thick Blanket Over the Capital

Satellite images showed a dense layer of smog hanging over northern India two days after Diwali, and visibility in the capital dropped sharply. Fine particulate matter, PM2.5, remained the dominant pollutant at most monitoring stations across the city. Research by the Centre for Research on Energy and Clean Air (CREA) found that Diwali 2026 was the fourth most polluted day of the entire year in Delhi, with a daily average PM2.5 concentration of 257 micrograms per cubic metre.

The pollution peak also exposed gaps in the monitoring network. According to CREA, 36 of the city's monitoring stations had no hourly PM2.5 data at 1 am on November 9, right when pollution levels were at their worst, and some stations maxed out at 1,000 micrograms per cubic metre, the ceiling displayed on the public portal.

Flights Delayed as Visibility Falls

The smog hit air travel hard. Delhi Airport activated its first Low Visibility Procedure of the 2026-27 winter season on Diwali night, and around 44 per cent of departing flights between midnight on November 8 and 8 pm on November 9 were delayed, with the average delay standing at about 20 minutes. Arriving flights were largely unaffected during the same period.

The disruption continued into Tuesday. A check of Flightradar24 data at around 12.45 pm on November 10 showed 197 delayed flights, about 14 per cent of the day's movements, and 32 cancellations, around 2 per cent, with an average delay of 13 minutes. The airport has issued passenger advisories and clarified that flight operations are continuing, with low-visibility procedures in place as a precautionary safety measure.

Emergency Curbs Already in Force

Stage III of the Graded Response Action Plan (GRAP), the emergency framework for Delhi-NCR, has been in force since November 6, after the Commission for Air Quality Management (CAQM) invoked the restrictions in anticipation of worsening air quality. The measures target construction dust, older vehicles and industrial emissions across Delhi and adjoining districts of Haryana, Uttar Pradesh and Rajasthan.

The Air Quality Early Warning System has pointed to a mix of causes behind the episode: unfavourable weather, vehicular emissions, Diwali celebrations and crop-residue burning. Outlook India reported 1,248 stubble-burning incidents across four states and the capital on Diwali, compared with 135 last year.

A Slight Improvement, but No All-Clear

There was some relief on Tuesday, November 10, as wind speed picked up. CPCB readings placed Delhi's overall AQI at around 304 in the morning, still in the very poor category, and later at 299, moving into the poor category. The forecast, however, offers no quick escape. The Air Quality Early Warning System expects air quality to remain very poor on November 10 and 11, and the India Meteorological Department has forecast no rainfall in Delhi until November 15.

For the city's nearly 30 million residents, the message from doctors remains the same every winter: stay indoors when the air turns grey, wear a mask outside, and keep children and elderly people away from early-morning outdoor activity.

Delhi's smog returns every winter, but this Diwali has made one thing clear again. Fireworks, stubble smoke and still winter air are a dangerous combination, and the emergency curbs alone have not been enough to keep the capital breathing easy.

What do you think should change first to fix Delhi's winter air: stricter firecracker rules, faster action on stubble burning, or cleaner transport? Tell us in the comments.