Aadi 18 or Perukku falls on the 18th day of the Tamil month of Aadi (Mid-July to mid-August). Water is celebrated on this day. A tribute is paid to water’s life sustaining property. This element of nature has been blessing mankind with peace, prosperity, and happiness. Worship of nature in the form of Devi is organised in order to shower bountiful grace on the human race. The day is connected with the annual freshets of water. This water raises the prosperity of the land.

The rivers, Ganga, Yamuna, Kaveri, and Godavari are considered to be most sacred among the rivers. Like earth which gives us food, water is also a basic necessity. People began to worship water in the form of wells, tanks, and rivers. They throw fruits, coconuts along with saffron dyed or turmeric dyed fabrics when the rivers are in spate. This is based on the belief that rivers are female goddesses.

Each and every temple has a sacred well or tank which is known as, Theppakkulam in Tamil. Serval cultural developments highlight the need for water and helps one understand that water culture and civilization represent human interest with sacredness. Mulaipari – germination of none grains in a basket, is an important ritual that takes place on Aadi 18. It is a women's-only ritual. The ladies carry the container in a position and dissolve it in the near by river. Special songs and dances (Kummipaatu) are performed. An icon of Devi accompanies these processions. This procession is a request to Devi and she blesses the people with rain and fertility of land. Large group of women are involved and this implies the fertility of women this day is meant to ensure the continuation of a human race with peace and harmony through empowered women.

Aadi Perukku is the time which welcomes joy and prosperity. Aadi Padhinettu (18) is said to announce the arrival of the monsoon. The volunteers at Siruthuli celebrate Aadi Perukku by offering prayers at the Chittirai Chavadi Checkdam, which is located on the river Noyyal in Coimbatore (India). This day is the Water Day for Tamil Nadu. Now a days, Aadi 18 is celebrated in order to spread awareness about the importance of water conservation. Pure water has become a rarity and a thought that water should be pure while found amidst nature is even rarer.

Young girls who celebrate this day by offering, Kaadholai (Earrings made of palm leaves), Karugamani (Blacks beads), and Kapparusi (A sweet made of hand pounded rice and jaggery) will be blessed with good husbands. Reverend communities spend the evening hours on Aadi 18 by the river. They enjoy themselves by consuming preparations of rice like Puliodharai, Thengasaadham, and Elumichaisaadham.

The cultural significance of this day is brought out quite well in Kalki's legendary novel, ‘Ponniyin Selvan.’ Aadi Perukku is used in the story for the purpose of introducing the protagonist to the readers. The hero of the book, Vandhiya Thevan drives through the shores of the Veeranam Yeri while enjoying the sights of the Aadi 18 celebrations. The daring Vandhiya Thevan has good with the villagers.

The Veeranam Yeri or lake was known as Veeranarayana Yeri. It was so named by the valorous Chola crown prince, Rajaaditya. A temple for Lord Vishnu is located on the banks of this lake and the Lord is known as Veeranarayana Perumal. The first Vaishnavaite Aacharya, Naada Muni was born here and his journey connected with the Sri Vaishnavaite Sampradayam began here. His grandson, Yamunaacharya also known as Aalavandaan was the Aacharya who identified the great Baashyakaara, Saint Ramanuja. The great saint was responsible for the construction of the Thondanur lake in Karnataka. The waterfall nearby is known as Ramanuja Gange. It must have been a wonderful sight to see Ramanujaacharya and his disciples thanking Lord Narayana while celebrating Aadi 18 on the banks of the Thondanur lake. The Hoysala ruler, Visnuvardana had constructed the Panchanarayana Kshetrams (Five temples for Lord Narayana) during the twelfth century along with a number of water bodies under the instructions of Ramanujaacharya. Ramanujaacharya had called it Thirumalasagara and it was also known as Yadavasamudra. A holy dip in the Ramanuja Gange waterfalls is said to cure people with skin disease. The lake created by Ramanujaacharya extends to over 2000 acres and there are 4 temples situated around it.

The day Aadi Padhinettu is important not just for the people of Tamil Nadu but also the people of Bharatavarsha at large.