Delhi records highest Diwali pollution level since 2021; AQI remains very poor next day

Delhi recorded its most polluted Diwali in five years, with the average Air Quality Index (AQI) reaching 376 on the day of the festival. Pollution levels remained high the following morning, with the overall AQI standing at 371 at 10 am on Monday as a thick layer of smog and fog covered the city.

The post-Diwali AQI was also the highest recorded on the day after the festival since 2021.

Of the 51 monitoring stations that reported data, 14 recorded air quality in the ‘severe’ category, four in the ‘poor’ category and the remaining 33 in the ‘very poor’ category. Delhi Technological University (DTU) recorded the highest reading at 439. The overall AQI had stood at 370 at 8 am.

According to Central Pollution Control Board (CPCB) data, Delhi’s Diwali-day AQI of 376 was the highest for the festival since 2021, when the index reached 382.

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Diwali falls on different dates in October or November each year. This year, the festival was celebrated on November 8, compared with October 20 in 2025, October 31 in 2024, November 12 in 2023, October 24 in 2022 and November 4 in 2021.

The average AQI on Diwali was 345 in 2025, 328 in 2024, 218 in 2023 and 312 in 2022. The corresponding figure was 382 in 2021 and 376 this year.

Pollution also remained high on the day after Diwali. The full-day average AQI on the post-Diwali day was 351 in 2025, 338 in 2024, 360 in 2023, 302 in 2022 and 462 in 2021.

Smog and fog reduce visibility across Delhi

The city woke up to dense smog and fog on Monday, with visibility dropping sharply at both of its major weather stations during the early morning hours.

At Safdarjung, visibility fell to 50 metres at 6.30 am, placing it in the dense fog category. This was significantly lower than the 700 metres recorded a day earlier. At Palam, visibility stood at 400 metres, indicating moderate fog, compared with 800 metres on Sunday.

Visibility improved to 100 metres at Safdarjung and 600 metres at Palam by 8.30 am. By 9 am, it had increased to 500 metres and 900 metres, respectively, with both stations reporting shallow fog, according to India Meteorological Department (IMD) data.

At Safdarjung, shallow fog was recorded between 10.30 pm and 2.30 am, before dense fog set in from 2.30 am to 9 am. The dense fog lasted six hours and 30 minutes. Shallow fog was reported again from 9 am.

At Palam, shallow fog was recorded from midnight to 5 am, followed by moderate fog between 5 am and 8.30 am. The moderate fog lasted three hours and 30 minutes, after which shallow fog was reported.

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“It is smog along with fog,” IMD officials said.

The officials attributed the drop in AQI from the previous night and the hazy conditions to dry weather and calm winds. Winds remained calm over Safdarjung and Palam during the previous evening, they said.

IQAir places Delhi in ‘very unhealthy’ category

Meanwhile, Swiss air quality monitoring platform IQAir placed Delhi in the ‘very unhealthy’ category on Monday morning, recording an AQI of 245 at 8.30 am.

According to IQAir, PM2.5 concentration stood at 170 micrograms per cubic metre, around 34 times the World Health Organisation’s annual guideline value.

PM10 concentration was recorded at 126 micrograms per cubic metre, while ozone levels stood at 31, nitrogen dioxide at 44.6 and sulphur dioxide at 32. Carbon monoxide concentration was recorded at 1,461.5 micrograms per cubic metre.

PM2.5 refers to fine particulate matter that can penetrate deep into the lungs and enter the bloodstream. It is among the major air pollutants of concern because of its adverse effects on health.

IQAir’s dashboard also displayed a prominent air quality alert for Delhi, with data from 32 monitoring stations provided by 12 contributors.

Separately, real-time readings on AQI.in showed Delhi’s AQI had climbed to 2,283 after Diwali. Six other Indian cities also recorded AQI levels above 1,000 at 9 pm on Sunday, according to the platform.

On Monday morning, AQI.in recorded Delhi’s air quality at 637 and classified it as ‘hazardous’.

Several parts of the capital, including Bawana, Burari, Jahangirpuri, Sonia Vihar, Punjabi Bagh, Okhla and Rohini, continued to record severe air quality on Monday. Pollution levels had remained high since Sunday night.

Firecrackers reported beyond permitted hours

Despite restrictions on firecracker bursting, fireworks continued in several parts of Delhi on Sunday evening. Reports emerged from Pitampura, Burari, Mayur Vihar and parts of Lutyens’ Delhi.

An order issued by the District Magistrate (East) had permitted the bursting of green firecrackers only on November 7 and 8, between 6 am and 7 am and 8 pm and 10 pm.

However, residents reported that firecrackers were burst beyond the permitted evening hours. The intensity of fireworks was particularly high in Pitampura and Burari in outer Delhi, as well as Mayur Vihar.

The district magistrate’s order also prohibited firecracker bursting within 300 metres of hospitals, nursing homes, health centres, old-age homes, educational institutions and other notified silence zones.

Only CSIR-NEERI-certified green firecrackers were permitted for sale, and only at locations designated by the Delhi Police in coordination with the district administration. The administration had also announced joint patrolling and enforcement teams to check unauthorised sales and the use of prohibited firecrackers.

Air quality forecast remains severe

According to the Air Quality Early Warning System (EWS), Delhi’s air quality is likely to remain in the severe category over the subsequent few days.

The EWS said a ventilation index below 6,000 square metres per second, combined with an average wind speed of less than 10 kilometres per hour, is unfavourable for the effective dispersion of pollutants.

Unfavourable weather conditions, vehicular emissions, Diwali celebrations and the ongoing peak stubble-burning season in neighbouring states are among the factors expected to contribute to the deterioration in air quality.

According to the CPCB, an AQI between 0 and 50 is classified as good, 51 and 100 as satisfactory, 101 and 200 as moderate, 201 and 300 as poor, 301 and 400 as very poor, and 401 and 500 as severe.

(With inputs from agencies)