Month of October and November are notorious for Delhi in the terms of increasing pollution levels. Weather plays an important role in increasing pollution over Delhi and NCR. By the end of September monsoon usually withdraws from northern plains. Humid easterly winds are replaced by dry westerly and North westerly winds.
Weather becomes dry and loose dust as well as other pollutants start mixing with air. Stubble burning also commence in central Pakistan, Haryana, and Punjab. Smoke of stubble burning reaches Delhi will the with the favorable direction of North westerly winds.
AQI of Delhi now is in moderate category. Westerly winds of will once again replaced by easterly winds due to the formation of a low-pressure area over East India which will subsequently move over Madhya Pradesh and western part of Uttar Pradesh as a cyclonic circulation.
Rain is also expected from night of October 16 which may last up to October 18. Moderate showers will wash away the pollutants and AQI may become comfortable.
Air quality index of Delhi NCR may reach to poor or very poor category by the end of October as the temperatures will start dropping leading to formation of haze and mist. Smoke of stubble burning along with local pollutants such as loose dust and smoke from vehicular traffic and factories will mix with the water vapor of haze and mist.