Delhi woke on Monday to its worst post-Diwali air in five years, with the city's average air quality index at 371 at 10 in the morning and 14 of the 51 monitoring stations that reported data already in the "severe" category, as a thick blanket of smog and fog refused to lift over the national capital.
The reading capped a grim festival weekend. According to Central Pollution Control Board data reported by the Press Trust of India, Delhi recorded an average AQI of 376 on Diwali day itself, Sunday, its most polluted Diwali in five years and the highest festival-day reading since 2021, when it stood at 382. The morning after was only marginally better, and the 371 recorded at 10am on Monday was the highest post-Diwali reading in four years, above the 351 of 2025, the 339 of 2024, the 358 of 2023 and the 302 of 2022.
The station-by-station picture was worse than the city average suggested. Of the 51 stations that recorded data on Monday morning, 14 were in the severe band, 33 in the very poor band and only four in the poor band. Delhi Technological University recorded the worst reading in the capital at 439. The Indian Express reported that eight stations had already crossed 400 by 9.05am, including Mundka at 425, Vivek Vihar at 421, North Campus at 419, Rohini at 417, Jahangirpuri at 415, the ITO at 414, Punjabi Bagh at 410 and Patparganj at 409.
The fine particles behind the haze reached extraordinary levels. The Indian Express analysis of hourly pollution data found that PM2.5 concentrations came close to 1,000 micrograms per cubic metre at some stations during the Diwali night. North Campus, monitored by the Indian Institute of Tropical Meteorology, recorded the highest hourly PM2.5 concentration at 998.90 micrograms per cubic metre, with its daily station average standing at 512.76. The hourly peak was more than 16 times India's national 24-hour safe limit of 60 micrograms per cubic metre and 66 times the World Health Organisation's 24-hour guideline of 15.
But the official figures themselves are now under scrutiny, because the severity of the pollution was likely worse than the published numbers suggested. Several monitoring stations went offline on Sunday night during the peak period of firecracker use, raising questions over the reliability of the air quality monitoring exercise. Private agencies painted a considerably worse picture: AQI.in recorded Delhi's air quality at 637 on Monday morning and said it had peaked at 2,283 after Diwali, while the Swiss platform IQAir recorded an AQI of 245 on the US scale at 8.30am, with PM2.5 concentrations at 170 micrograms per cubic metre, around 34 times the WHO's annual guideline value. Experts quoted in the reports questioned why the gaps appeared exactly when pollution was at its worst.
The numbers have already become a political row. The Aam Aadmi Party alleged data fraud over the missing readings, while the BJP fired back over what it called a Punjab stubble-burning conspiracy, in a familiar blame game that surfaces every winter as Delhi's air turns toxic. The dispute centres on how much of the spike came from Diwali firecrackers, how much from farm fires in Punjab and Haryana, and how much from the calm, cold air that traps pollution over the city each November.
Health experts warned that the risks are not limited to people with existing breathing problems, with even healthy residents reporting symptoms as the toxic haze settled over the city. Hospitals were also dealing with the other side of the festival: Safdarjung Hospital recorded 135 Diwali-related burn cases over two days, including 129 firecracker injuries and six involving oil lamps, while AIIMS reported 42 Diwali-related burn injuries up to Monday.
Delhi was not alone. Air quality deteriorated across north India after the festival, with AQI levels in Delhi, Haryana, Punjab and western Uttar Pradesh well above 350, in the very poor range. Mumbai and Chennai also woke to a smoggy morning after Deepavali, and Mumbai's civic body reported 137 firecracker-related fires in a single day, the highest single-day toll in years, leaving two women injured.
By late afternoon the capital had improved only slightly, with the average AQI falling to 344 by 4pm, compared with 376 at the same time on Diwali day. Bawana recorded the highest reading at that hour at 396, followed by Burari at 393. According to the Air Quality Early Warning System, Delhi's air quality is likely to remain in the severe category over the subsequent few days, with the smog and fog expected to linger.
The coming days will show whether the city gets any relief and whether the monitoring gaps are explained. What is already clear is that Delhi has had its dirtiest Diwali in five years, that the worst readings of the weekend may never have been officially captured, and that the annual post-festival pollution crisis has arrived in full force once again.
Figures in this report were checked at 19:58 PKT on 09 November 2026 against reports from the Press Trust of India, the New Indian Express, the Economic Times, the Indian Express and The Hindu.
