Delhi’s winter of 2025 revealed a harsh and unexpected reality: Delhi-NCR saw worse smog in December than in October and November, which are usually blamed for stubble burning. The city registered an average Air Quality Index (AQI) of349 in December 2025, according to the Central Pollution Control Board (CPCB), the highest December AQI in at least 7 years and a significant increase from 294 in December 2024.

In addition, the CPCB report indicates that farm fires accounted for only about 3.5% of PM2.5 pollution in early December, suggesting that crop residue burning had almost no impact on pollution during the month, even though it was historically considered the leading cause of winter smog.

December 2025 vs. Stubble Burning Season

Based on real-time air quality stations and modeling, the CSE analysis of the Centre for Science and Environment (CSE) suggests that the average particulate matter with a diameter of less than 2.5 micrometers (PM2.5) concentration in December was 210 µg/m³, which is about 29% higher than the stubble season average (~163 g/m).

To understand the shift in pollution patterns, here’s a comparison of key air quality measurements during the stubble-burning season (October-November) and in December:

These numbers indicate that the smog in Delhi was worse in December, not because of increased farm fires, but because other sources of pollution continued to release harmful substances into the air, while winter weather conditions trapped the pollutants.

Also Read: Delhi Braces For Prolonged ‘Very Poor’ Air As Pollution Levels Stay High

December Air Quality Reached Multi-Year Extremes

One of the most convincing pieces of evidence that the Delhi-NCR saw worse smog in December is the official air quality monitoring conducted by the Central Pollution Control Board (CPCB). The Central Pollution Control Board recorded the worst air quality in the national capital in December 2025 since at least 2018. It reported an average Air Quality Index (AQI) of 349 for December 2025. It is worth mentioning that this heavy pollution occurred when farm fires (stubble burning) accounted for only ~3.5% of PM2.5 levels during the month, which is much lower than in October and November.

The daily observations show an even clearer picture: on a few days in the middle of December, Delhi’s AQI went above 400 (the ‘severe’ category), and several stations regularly recorded values in the range of 400 to 460. Many areas, including Nehru Nagar, Mundka, and Chandni Chowk, recorded AQI levels above 450 on those days, indicating hazardous air quality.

Also Read: Manjinder Singh Sirsa Says Delhi Recorded Its Best Air Quality In Eight Years In 2025

PM2.5 Concentrations Far Exceeded Health Standards

Delicate particulate matter (PM2.5), the most harmful air pollutant, showed extreme elevation. Based on analysis by CPCB, Delhi’s average PM2.5 concentration in December was ~211 µg/m³, which is:

• 3.5 times the Indian 24-hour safe limit (60 µg/m³)
• 8 times the WHO guideline (25 µg/m³)

Several monitoring stations, including Mundka, Nehru Nagar, and Anand Vihar, repeatedly recorded values of 300–450 µg/m³ during smog episodes in mid-December. This represented a 28-30% increase in PM2.5 levels compared to November, even though agricultural fires had dropped sharply.

Also Read: Wildfire Air Pollution Far Greater Than Previously Estimated, Study Finds

Stubble Burning Contribution Dropped to Marginal Levels

In December, the impact of stubble burning on air pollution was at its lowest levels, in stark contrast to what people assume. Farm fires, as per CSE and SAFAR data, were responsible for only 35% of the PM2.5 levels in Delhi during December, while:

• They were responsible for 15-22% on peak-burning days in early November.
• Around 10% as a seasonal average in past years.

The number of fires detected by satellites in Punjab and Haryana has dropped by more than 80% after the middle of November. Nevertheless, pollution worsened, Delhi-NCR saw worse smog in December, and the main reasons for this were non-agricultural sources.

Also Read: Are Air Purifiers Worth It? Why Cleaner Indoor Air Matters For Families With Babies

How to Control Delhi’s Air Pollution?

• Strengthen public transport and reduce private vehicle use by expanding metro, electric buses, and last-mile connectivity

• Strictly control construction dust and road dust through mandatory coverings, water sprinkling, and regular road vacuuming

• Accelerate transition to clean energy by phasing out coal and diesel generators and promoting rooftop solar

• Tackle stubble burning at source by supporting farmers with incentives, machinery, and alternatives to crop residue burning

• Improve real-time monitoring and enforcement using data-driven action plans and penalties for major polluters

Also Read: Ghaziabad Ranked India’s Most Polluted City In November 2025: CREA Report

Conclusion

The fact that Delhi-NCR saw worse smog in December than during the stubble-burning months changes our understanding of air pollution in northern India. While controlling farm fires is still important, dealing with city pollution, the movement of pollutants from other areas, and the effects of winter weather is also essential.

This situation shows that simple, one-sided solutions are not enough. Delhi and its surrounding areas need a complete, science-based, long-term plan that reduces pollution from all major sources, improves public transportation and energy use, and coordinates actions across state borders. Only then can the region hope to have cleaner air, not just in December, but throughout the year.

Also Read: How To Prevent Mold And Improve Indoor Air Quality

FAQs

1. Why was the smog in Delhi worse in December, even after stubble burning ended?

Winter weather conditions trap pollution from local and regional sources, such as vehicles, industries, and dust. These sources can produce more pollution than agricultural smoke once stubble burning decreases.

2. Does this mean stubble burning is not harmful?

No. It still contributes to pollution in October and November. However, the data from December shows that air pollution comes from many sources, not just farm fires.

3. What can be done to improve air quality in Delhi?

Year-round pollution controls, cleaner vehicles and fuels, changes in industrial practices, waste and dust management, and regional collaboration are all needed to achieve lasting improvement.

Also Read: Nine Million Deaths Linked To Air Pollution Each Year As Rising Temperatures Degrade Air Quality