Why is the Air Pollution in Delhi is high in every October

Monsoon withdrawal in October in northwest India changes wind direction from easterly to north westerly, which constitutes 72% of Delhi's winter winds. Storms carrying dust arrive from Rajasthan and sometimes Pakistan. Temperature dips lower the inversion pollutants. Farm fires also play a role in Delhi's height, the layer beyond which pollutants cannot disperse, leading to increase in pollution.