It is worth noting that Diwali falls on different days in October or November every year. It was on November 8 this year, on 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 stood at 345 in 2025, 328 in 2024, 218 in 2023 and 312 in 2022, compared with 382 in 2021 and 376 this year.
The pollution levels remained high on the day after the festival as well. The full-day average AQI on the day after Diwali was 351 in 2025, 338 in 2024, 360 in 2023, 302 in 2022 and 462 in 2021.
The city woke up to a thick layer of smog and fog on Monday, with visibility dropping sharply at both of Delhi’s major weather stations during the early morning hours.
At Safdarjung, visibility dropped to 50 metres at 6.30 am, placing it in the dense fog category, compared with 700 metres a day earlier. At Palam, visibility stood at 400 metres, indicating moderate fog, against 800 metres on Sunday.
At 8.30 am, visibility improved to 100 metres at Safdarjung and 600 metres at Palam. It subsequently improved to 500 metres and 900 metres, respectively, by 9 am, with both stations reporting shallow fog, according to India Meteorological Department (IMD) data.
At Safdarjung, shallow fog was observed between 10.30 pm and 2.30 am before dense fog set in from 2.30 am to 9 am, lasting six hours and 30 minutes. Shallow fog was reported again from 9 am.
At Palam, shallow fog was recorded between midnight and 5 am, followed by moderate fog from 5 am to 8.30 am, lasting three hours and 30 minutes. Shallow fog was subsequently reported from 8.30 am.
“It is smog along with fog,” IMD officials said.
The officials attributed the drop in AQI from last night and the hazy conditions to dry weather and calm winds. Winds remained calm over Safdarjung and Palam during the previous evening, they said.
Meanwhile, Swiss air quality monitoring platform IQAir placed Delhi’s air quality in the ‘very unhealthy’ category on Monday morning, recording an AQI of 245 at 8.30 am.
According to IQAir, the concentration of PM2.5 stood at 170 micrograms per cubic metre, around 34 times the World Health Organisation’s annual guideline value.
The concentration of PM10 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, fine particulate matter capable of penetrating deep into the lungs and entering the bloodstream, is among the major pollutants of concern due to its adverse health effects.
IQAir’s dashboard also showed a prominent air quality alert for Delhi, with data from 32 monitoring stations provided by 12 contributors.
Meanwhile, real-time readings on AQI.in showed that 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, classifying it as ‘hazardous’.
Several areas, including Bawana, Burari, Jahangirpuri, Sonia Vihar, Punjabi Bagh, Okhla and Rohini, continued to record severe air quality on Monday, with pollution levels remaining high since Sunday night.
Despite restrictions on firecracker bursting, several parts of Delhi continued to witness fireworks on Sunday evening, with reports emerging from areas including Pitampura, Burari, Mayur Vihar and parts of Lutyens’ Delhi.
The District Magistrate (East), in an order, 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 continued to be burst beyond the permitted evening window. In outer Delhi’s Pitampura and Burari, Mayur Vihar, the intensity of fireworks was particularly high.
The DM’s order also prohibited the bursting of firecrackers 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, exclusively at locations designated by the Delhi Police in coordination with the district administration, which had also announced joint patrolling and enforcement teams to check unauthorised sale and use of prohibited firecrackers.
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.
A ventilation index below 6,000 square metres per second, coupled with an average wind speed of less than 10 kilometres per hour, is unfavourable for the effective dispersion of pollutants, according to the EWS.
Unfavourable meteorological 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.
According to the Central Pollution Control Board (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.
