Pollution levels in Delhi this December were the lowest in the last four years, according to the Central Pollution Control Board (CPCB).
The average air quality index (AQI) for December stood at 308. It was 337 last year, 360 in 2018 and 316 in 2017, the CPCB data showed.
The capital recorded four "severe" air quality days this December as compared to eight each in 2019 and 2018 and one in 2017.
There were 10 "poor" air days this December as against seven, four and nine in 2019, 2018 and 2017, respectively.
The city recorded a peak AQI of 433, which is also the lowest in four years. In December 2019, the peak AQI was 446. It was 450 in 2018 and 469 in 2017.
Kuldeep Srivastava, the head of the regional forecasting centre of the India Meteorological Department, said strong winds, courtesy western disturbances, led to better air quality this December as compared to previous years.
High daytime temperature led to better ventilation conditions. Light rainfall under the influence of western disturbances also washed away the pollutants, he said.