Diwali Pollution: Delhi-NCR Struggles to Recover as Southern Cities Clear the Air Faster

A three-year analysis of daily CPCB National Air Quality Index (AQI) bulletins across nine Indian cities has revealed a striking difference in how quickly cities recover from Diwali-related pollution.

While Delhi, Gurugram, Lucknow and Patna experienced prolonged pollution episodes, southern and coastal cities such as Chennai, Hyderabad, Bengaluru and Mumbai generally recorded faster post-festival recovery.

The study compares seven-day pre-Diwali and post-Diwali AQI averages with the two-day Diwali window across 2024, 2025 and 2026.

City-wise AQI comparison: 2024–2026

The following table presents mean daily AQI across the three measurement windows and the percentage change between pre-Diwali and Diwali averages.

AQI windows: Pre-Diwali (D-7 to D-1); Diwali (D and D+1); Post-Diwali (D+2 to D+8). Post-Diwali 2026 data was not yet available as the dataset ended on November 9, 2026.

Key findings

• Delhi: Diwali-window average AQI increased from 334 in 2024 to 360 in 2026. Its pre-Diwali average itself reached 347 in 2026.
• Gurugram: Recorded Diwali-window averages above 300 in all three years.
• Patna: Registered a 110% increase in AQI during Diwali 2026, among the highest relative spikes in the study.
• Chennai: Recorded the largest relative increase, at 139% in 2026, despite demonstrating faster post-Diwali recovery in 2024 and 2025.
• Mumbai: Its post-Diwali average fell dramatically to 71 in 2025, compared with a pre-Diwali average of 129.
• Hyderabad and Bengaluru: Maintained comparatively lower AQI levels, although both recorded their largest relative Diwali increases in 2026.
• Chandigarh: Its pre-Diwali average improved from 191 in 2024 to 82 in 2026.

Why does northern India take longer to recover?

The Indo-Gangetic Plain faces unfavourable atmospheric conditions after the monsoon. Falling temperatures, lower mixing heights, temperature inversions and calm winds trap pollutants close to the ground.

Crop-residue burning in Punjab and Haryana adds to the regional pollution burden. Consequently, Diwali fireworks compound an already deteriorating air-quality situation.

In contrast, Mumbai and Chennai benefit from coastal sea breezes, while stronger winds over the Deccan help disperse pollutants in Hyderabad and Bengaluru. Seasonal rainfall also helps Chennai clear particulate matter.

Two distinct pollution patterns

The analysis points to two different pollution regimes. Northern cities experience prolonged seasonal pollution, with Diwali adding to an already high baseline. Southern and coastal cities generally experience sharper but shorter-lived festival-related spikes.

The findings underline the need for region-specific air-quality management. While controlling firecracker emissions is important, tackling persistent pollution sources, particularly crop-residue burning, vehicular emissions, industrial pollution and construction dust, remains critical.

The central takeaway: Diwali fireworks may trigger pollution spikes, but geography, weather and year-round emission loads determine how long Indian cities take to breathe easier.

The writer of this article is Dr. Seema Javed, an environmentalist & a communications professional in the field of climate and energy