Pondicherry is a beach territory filled with lot of beaches to visit. Best time to visit is between December to March, where rains complete and winter sets in, summer is not an ideal time to travel to Pondicherry. But, some beaches have cool air that evenings appear warm though not hot.
I think it would be around 37°C.Summers (April-June) in Pondicherry are quite hot and the temperature touches 40 degrees Celsius. I think May is not a good season to visit pondicherry