TL;DR: AQI rose in 209 of 276 cities and towns with comparable readings between the Diwali and post-Diwali bulletins in 2026. Among the nine major cities examined, Pune saw the biggest rise, while Delhi’s AQI fell but remained Very Poor. Historical data shows a recurring seasonal pattern in Delhi, where nearly half of the days with readings from November to February were in the Very Poor category.

Context:

As the monsoon recedes and winter approaches, air quality in Delhi often begins to deteriorate. Winds weaken, and pollutants from traffic, agriculture stubble burning, industry and other sources tend to linger. Diwali falls during this seasonal transition, when emissions from fireworks can add to the pollution already in the air.

This year, concerns about Delhi’s air quality intensified ahead of the celebrations. On 6 November 2026, two days before Diwali, the city recorded an Air Quality Index (AQI) of 382, in the ‘Very Poor’ category. The Commission for Air Quality Management invoked Stage III of the Graded Response Action Plan across the National Capital Region that day.

Against this backdrop, we examine how air quality changed around Diwali in Delhi and eight other Indian cities, and how those readings compare with previous Diwalis and the longer seasonal pattern.

Who compiles this data?

The Central Pollution Control Board (CPCB), under the Ministry of Environment, Forest and Climate Change, compiles and publishes city-wise Air Quality Index (AQI) data for cities and towns across India on a daily basis. The report covers each city’s AQI, the corresponding air quality category, the prominent pollutant or pollutants, and the number of monitoring stations used to calculate the index.

Where can I download clean & structured data related to it?

Cleaned, structured, and ready-to-use dataset on the daily Air Quality Index (AQI) for major cities and towns across India can be downloaded from Dataful. The dataset is organised by date, state and area, and is updated daily with the latest available readings.

Key Insights:

We examine CPCB’s city-level AQI readings for Mumbai, Delhi, Kolkata, Chennai, Bengaluru, Hyderabad, Ahmedabad, Pune and Surat. These cities were selected based on the population ranking of their urban agglomerations in Census 2011.

Further, for this analysis, pre-Diwali, Diwali and post-Diwali refer to the CPCB bulletins for the day before, the day of and the day after the festival. For instance, in 2026, these correspond to 7, 8 and 9 November.

• Delhi had the highest AQI on all three days this year and remained in the Very Poor category. Its reported AQI rose from 369 on 7 November to 376 on Diwali day, then fell to 344 on 9 November. It is noteworthy that the number of stations contributing to the reported AQI fell from 59 on 7 and 8 November to 47 on 9 November.

• Pune and Bengaluru saw the biggest increases between the Diwali-day and day-after bulletins this year. From 8 to 9 November, Pune’s AQI rose from 163 to 292 (+129 points), moving from Moderate to Poor. Bengaluru’s rose from 70 to 133 (+63 points), moving from Satisfactory to Moderate. AQI rose in seven of the nine cities over this window, with declines in Delhi and Kolkata.

• Across the full three-day period in 2026, Pune and Chennai saw the largest increases. From 7 to 9 November, Pune’s AQI rose by 135 points and Chennai’s by 125 points. Chennai ended at 199, just below the Poor category. Pune, Ahmedabad and Surat moved from Moderate to Poor, taking the number of cities with Poor or worse air from one on 7 November to four on 9 November.

• In five cities, AQI was higher post-Diwali than pre-Diwali every year from 2022 to 2026. This pattern held in Ahmedabad, Bengaluru, Chennai, Hyderabad and Mumbai. Delhi followed the same pattern through 2025, before recording a decline in 2026.

• Kolkata and Pune saw a more mixed pattern. Kolkata’s AQI fell from pre-Diwali to post-Diwali in three of the five years. Pune saw declines in 2024 and 2025, followed by a rise in 2026 to its highest post-Diwali reading in the five-year comparison.

• Delhi recorded Very Poor air on nearly half of the days with readings from November to February. The share was 48.3% in those months, compared with 4.2% from March to June. This comparison uses all available readings from May 2015 to 9 November 2026.

• Poor or worse air was also more common from November to February in Kolkata and Surat. In Kolkata, the share of recorded days with AQI above 200 rose from 2.3% in March–June to 47.7% in November–February. In Surat, it rose from 5.7% to 23.0%. Bengaluru stayed below 1% in both periods.

• Delhi, Kolkata and Surat recorded the most Poor-or-worse days when all nine cities were compared on the same dates. Across the 1,134 dates with readings for all nine cities between January 2023 and 9 November 2026, AQI exceeded 200 on 42.2% of days in Delhi, 9.2% in Kolkata and 8.6% in Surat. Bengaluru and Hyderabad had no days above 200 on those shared dates.

• AQI rose in about three out of four monitored locations across India after Diwali. Among the 276 cities and towns with comparable readings, AQI increased in 209 between the Diwali and post-Diwali bulletins. The number reporting Poor or worse air rose from 69 to 123.

• The highest post-Diwali AQI readings were concentrated in northern India. Haryana, Uttar Pradesh and Rajasthan accounted for 23 of the 30 locations that recorded Very Poor air on 9 November. Bahadurgarh in Haryana had the highest reading in the comparison, at 400. Poor or worse air was also recorded in parts of Maharashtra, Odisha and Andhra Pradesh.

Why Does It Matter?

Delhi’s AQI fell in the post-Diwali bulletin, even as air quality worsened in about three-quarters of the monitored cities and towns with comparable readings. Looking beyond the capital changes the picture. Looking beyond Diwali does too. In Delhi, Kolkata and Surat, poor air was far more common from November to February than from March to June.

The seasonal pattern gives authorities a reason to plan pollution-control measures before air quality deteriorates and sustain them through winter.

Key numbers

• Cities and towns with Poor or worse air — 69 → 123, Diwali → post-Diwali 2026 (+54 locations).

• Pune’s AQI — 163 → 292, Diwali → post-Diwali 2026 (+129 points).

• Delhi’s AQI — 376 → 344, Diwali → post-Diwali 2026 (−32 points, Very Poor on both days)

• Delhi’s share of recorded days with Very Poor air — 4.2% → 48.3%, March–June → November–February (+44.1 percentage points).