The Panguni Uthiram festival falls in the month 'Panguni'
(March-April). This month is special because of the star 'Uthiram' and
'Pournami' occurring together. Besides, it is on "Panguni Pournami
Uthiram" that the marriage of Parvati and Parameshwara, Muruga and
Devasena, and Andal (also known as 'Kothai') and Rangamannar (also splet
as Rangamannar) took place.
Also, Valmiki's Ramayan (also spelt as Ramayana) says it is on this day and star that Sita's marriage with Rama was celebrated. From Brahmanda Purana one learns that on Panguni Uthiram every holy water joins Thumburu Teertha (also spelt as Tirtha), one of seven sacred tanks in Tirupati Tirumala.
The ancients chose Uthiram to convey to humans that it is for underlining the glory of Grahasta Dharma (married life) that the Almighty manifests in the marital state as Uma Maheshwara, Sita Rama, and Radha Krishna - despite his changelessness, sans childhood or youth or old age. The Lord is indeed a "Nitya Kalyana Murti". It is our duty to celebrate this day when the Lord, in both Shiva and Vishnu temples, appears to devotees in his married state.
On Panguni Uthiram, in all places where Lord Subramanya has a temple, his devotees carry in a Kavadi the requisites of puja for him, in fulfilment of vows. Such vow fulfilment by devotees carrying Kavadis is a special feature of Subrahmanya temples wherever they happen to be.
Devotees flock in hundreds to the Perur temple near Coimbatore during the Panguni Uthiram festival, which is celebrated in March every year.