The patroness of Terrasini is Maria Santissima delle Grazie, celebrated on 8 September; she has been so since 1653. There is also a date the town has carried with it for three centuries: on the night of 1 September 1726 a disastrous earthquake struck Palermo, killing more than two hundred people. Terrasini came through unharmed, and the miracle was attributed to the intercession of its patroness: on 22 September of that year the Archbishop of Palermo ordered that every year, on the night between 1 and 2 September, the bells should ring out in memory of the danger escaped, and Baron La Grua established that Terrasini should do the same.
On Easter day, instead, it is the turn of the Festa di li Schietti, attested as early as around 1850-1860: a committee of bachelors takes turns at lifting, with one hand only, a melangolo — a bitter orange tree.
