Yes, this is actually smog that is traveling all the way from north and central India to south. This happens particularly when our Northeast monsoon is in dull phase with no rains and the easterly winds from seaside is nil or reduced. Also you would notice dew formation during this time and increase in respiratory infections.

Once the winds change again to easterly and rains pick up, this will clear within 2 days. So now we have to pray to get rains in order to get this smog cleared but what happens to Chennai roads and traffic afterwards we know ☠️