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Why Indian Winter Air Quality is Worse than Summer


Winter AQI is not better than summer AQI

Just like a familiar winter guest, air pollution sweeps into India, casting a smoggy spell over its cities. Residents have grown accustomed to navigating through thick blankets of smog, relying on home air purifiers and outdoor masks to breathe amid this seasonal haze.

bad visibility in Delhi due to air pollution in winters

Analyzing India’s Summer & Winter Air Quality & Pollution Levels


Curious about the severity of the situation, we delved into the pollution data of five major Indian cities—New Delhi, Kolkata, Mumbai, Chennai, and Hyderabad. The focus? Winter, the season when the air quality takes a noticeable hit.


pollution levels across India on a map - summer and winter comparison


Ever wondered if one season reigns supreme in the pollution battle? We, at UBreathe, dug into the data across Chennai, Hyderabad, Kolkata, Mumbai, and New Delhi's air pollution levels across seasons;

we found the Winter season losing the battle.




Here's the Breakdown:

Two years of data from the US Embassy and consulates, dividing it into winter, summer, monsoon, and post-monsoon.


Seasonal Variation in PM 2.5 chart

Average PM2.5 levels

Winter: 118 micrograms, Summer: 49 micrograms.

That's a 26% drop in summer!


With Chennai usually being at the bottom of this list, it ended up surpassing the WHO limits at 31 micrograms. It's safe to say that summer AQI would be marginally better that the AQI during winter in India. However, this level of air quality is still far from being 'clean'.


The Reasons for Low Winter Air Quality in India


  1. In winter, air quality worsens due to unique air interactions. Cooling of the earth's surface creates a dense layer of cool air trapped under warmer air, known as a "temperature inversion." Limited air mixing traps pollutants near the ground, suffocating cities with their pollution.


A graphical representation of temperature inversion

2. Diwali, a vibrant festival celebrated in India during October and November,

marks the beginning of the new year. However, the joyous occasion is accompanied by the bursting of firecrackers, which unfortunately leads to a significant surge in air pollution levels. Consequently, the already chilly Indian winters witness a further rise in PM2.5 levels, exacerbating the situation.


Comparison of Diwali & Delhi's Air Quality

3. A major reason for the winter pollution comes from 'stubble burning' practices prevalent in the North Indian states.

Many farmers rotate between crops, planting rice in May and wheat in November. In order to quickly prepare their fields for the wheat crop, many farmers simply burn leftover plant debris after harvesting rice. The practice is known as paddy stubble burning. - NASA Earth Observatory

India's Winter Pollution Levels Compared With Summer


India's winter PM2.5 levels stand at an alarming 59% higher than those in summer. Delhi exhibits the most significant seasonal variation, while Chennai records the lowest.

The conclusion? The evidence is quite clear: summer air is better than winter air. However, despite all the blue skies and warm days, we’ve been having lately, there’s still a need to protect yourself inside and outside the house. Here, we must not mistake“better” for “safe.” Neither summer nor winter air quality in India meets the WHO health standards and summer air is still of significant concern to public health.


Share your thoughts: Which season do you find it easier to breathe?

Let's keep the conversation going about clean air!

Let's keep pushing for clean air, every season, everywhere!



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