The flag hoisting for the annual festival at the Annai Vailankanni Church in Besant Nagar is scheduled to happen this evening.
Pilgrims are already walking down the main roads, mostly from north and central parts of the city to participate in this event. As they pack into the pavements and spill on to the roads, traffic may be affected this afternoon onwards in San Thome, Alwarpet and R A Puram.
So if you have to travel to that part of the city, make your plans accordingly.
The main event, to celebrate the Nativity of Mother Mary, falls on next Friday, Sep 8. Pilgrims will again throng the roads and traffic diversions will be in place that day.