India is one of the most polluted countries in the world. In general, pollution is
more intense in the north, ie in the Indo-Gangetic plain, and in particular in large cities (see New Delhi). In the south, pollution is less intense because sea air masses circulate more easily.
As for the seasons, in the north, pollution reaches its maximum in the dry season, and in particular
from mid-October to February, when air stagnates more easily.
In the period preceding the monsoon, from April to mid-June, the concentration of particulate matter (PM2.5 and PM10) decreases a little, but the amount of ozone increases, which reaches its maximum in April, May and October (i.e. in the first month after the monsoon).
The period in which pollution is lowest is that of the monsoon, from July to September, due to the presence of low pressures, wind and rain.
Outside the Indo-Gangetic plain too, pollution is higher in large cities and in the dry period (which, as we have seen, is not the same everywhere).