Delhi's air quality during Diwali has consistently worsened over the past three years, with the average Air Quality Index (AQI) reaching 360 in 2026, up from 334 in 2024. This persistent decline, placing the capital firmly in the 'Very Poor' category, raises significant concerns about the effectiveness and timing of existing pollution control measures.
Diwali AQI Trends Show Deterioration
An analysis by Climate Trends, titled "Factors Determining Post-Diwali AQI Recovery Rates in Different Indian Cities: A Three-year Analysis (2024–2026)," revealed a steady increase in Delhi's average Diwali AQI. It rose from 334 in 2024 to 348 in 2025, culminating in 360 in 2026.
Crucially, the study highlighted that Delhi entered Diwali 2026 with an alarming average AQI of 347 in the preceding week, significantly higher than 295 in 2024 and 242 in 2025. This indicates that the city is already experiencing severe pollution before the festival's firecracker emissions contribute further.
Peak AQI levels during the Diwali period also showed an upward trend, hitting 376 in 2026, compared to 351 in 2025 and 339 in 2024.
Why Pollution Controls Are Falling Short
The study suggests that focusing solely on firecracker bans is insufficient to tackle Delhi's chronic winter pollution. Several factors contribute to the persistent 'Very Poor' air quality:
- Atmospheric Stagnation: Post-monsoon conditions lead to low wind speeds and temperature inversions.
- Crop-Residue Burning: Agricultural burning in neighboring Punjab and Haryana contributes significantly to particulate matter across the Indo-Gangetic Plain.
These conditions mean pollution often lingers well after Diwali. For instance, in 2024, Delhi's average AQI worsened from 334 during Diwali to 366 in the subsequent week. In 2025, post-Diwali levels remained elevated at 304.
Southern Cities Show Faster Recovery
A stark contrast was observed when comparing northern and southern Indian cities. Chennai and Hyderabad, for example, returned to or below their pre-Diwali AQI levels within a week in both 2024 and 2025. Researchers attribute this faster recovery to environmental factors like coastal sea breezes, stronger winds over the Deccan plateau, and seasonal rainfall, which aid in pollutant dispersal.
"The key takeaway is that a short-term pollution spike need not translate into a prolonged episode," stated Dr. Palak Balyan, Research Lead at Climate Trends.
Recommendations for Effective Management
To address the worsening trend, the study recommends a shift towards proactive, rather than reactive, pollution control:
- Early Interventions: Implement Graded Response Action Plan (GRAP)-type measures and crop-residue burning controls before Diwali, rather than waiting for pollution levels to escalate.
- Region-Specific Strategies: Develop tailored air quality management plans for different regions.
- Enhanced Monitoring: Strengthen the monitoring of various pollution sources throughout the year.
While the analysis did not statistically isolate the impact of firecracker emissions from other factors, its findings underscore the urgent need for comprehensive, year-round strategies to combat Delhi's severe seasonal air pollution.