Delhi Records Cleanest December Air Since 2015, Driven By Strong Winds And Record Rainfall

Delhi experienced its cleanest December air since 2015, recording an average AQI of 294. This significant improvement was driven by strong winds in early December and record-breaking rainfall in the latter half of the month, according to officials. Data from the Central Pollution Control Board (CPCB) also revealed that December 2024 marked Delhi’s cleanest first half ever, with only one "very poor" air quality day recorded between December 1 and 15. 

The lowest AQI of the month, 139, was observed on December 28, making it the cleanest December day on record. Additionally, the average AQI during the month stood at 238, a marked improvement compared to December 2023’s 348 and the historical December average of over 300.

The AQI on Tuesday stood at 230 "poor", with localized spikes above 300 in areas like Jahangirpuri and Vivek Vihar. However, Monday’s AQI was 173 ("moderate"), reflecting a significant improvement from Sunday’s 225 "poor". 

This month saw eight "moderate" air quality days, a record compared to previous Decembers, which rarely exceeded three such days. The highest AQI of the month, 451 ("severe"), was recorded on December 19 during a period of stagnant air caused by a western disturbance.

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Since 2015, Delhi’s December AQI has averaged over 300, with previous lows of 300 in 2015 and 319 in 2022. This year’s cleaner air highlights a significant deviation from the trend, aided by favourable weather patterns.

Experts attributed the improved air quality to efficient pollutant dispersion early in the month, although the third week saw a slowdown in winds, resulting in six "severe" air quality days between December 17 and 23. Mahesh Palawat of Skymet noted that early December’s winds prevented pollutant accumulation and dense fog, ensuring relatively clean air conditions.

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Delhi December Rainfall

Delhi witnessed 53.5 mm of rainfall this December, making it the fifth-wettest December since 1901. Notably, 41.2 mm of rainfall occurred on December 28, the highest single-day December rainfall in 101 years. In contrast, December 2023 and 2022 saw no rainfall, while December 2021 recorded 9.6 mm. Strong winds during the first two weeks of December effectively dispersed pollutants, maintaining cleaner air and preventing dense fog.