Delhi’s Air Quality Index (AQI) remained in the “very poor” category on Saturday, December 20. The AQI was recorded at 376 early Saturday morning compared to 374 recorded on Friday.
Dense fog is likely to worsen Delhi’s air quality over the weekend, officials told PTI, despite strict pollution control measures being put in place.
According to the CPCB classification, an AQI between 0 and 50 is considered “good”, 51–100 “satisfactory”, 101–200 “moderate”, 201–300 “bad”, 301–400 “very bad” and 401–500″.
Meanwhile, the India Meteorological Department (IMD) has issued a yellow fog alert and predicted dense fog on Saturday, December 20. Fogs are likely to persist through the early hours of the coming days as the cold weather intensifies, according to forecasters.
When is the AQI expected to improve in Delhi?
Shambhavi Shukla, program manager at the Center for Science and Environment in New Delhi, told Mint that Delhi’s air quality is likely to improve from February and March onwards.
“The air quality is not good, but better than what’s happening right now,” she said, adding that as the year goes on, with the monsoon coming from late July and August onwards, “then you can see the best air quality.”
AQI trend from January 1, 2025 to November 30, 2025.(BAILIFF)
What leads to improved air quality?
Shambhavi Shukla explained that when it rains, all the particles settle. She said that as of now there is fog (water droplets and moisture in the air) and particulate matter (PM 10 and PM 2.5).
Especially during the monsoon when there is rain, these particles settle and “you can see less dust/particles and it washes the pollution out of the air,” Shukla said.
Air pollution, fog in winter
Heavy air pollution and fog during winter are persistent problems, posing significant health risks and disrupting daily routines around the world.
studies, with the name “Role of meteorology and air pollution on fog conditions over Delhi during peak winter 2024” investigated the conditions favoring long-lasting fog in Delhi during January 2024 using observations, backtrajectories and reanalysis datasets.
An analysis of visibility observations revealed that fog persisted in Delhi for 46 percent of the time during the period under review.
The existence of three to four days of cold wave to severe cold wave conditions and the lack of passage of strong western disturbances over north and northwest India also favored prolonged fog formation.
In addition, high relative humidity, shallow boundary layer, stable weather conditions such as absence of significant surface winds, existence of cold wave to strong cold wave, temperature inversion (up to 4 °C), poor ventilation and presence of high particulate matter (PM10 and PM2.5) facilitated fog formation.
