Aadi is the fourth month in the Tamil Calendar - the period from mid July to mid August and is called Ashada in Karnataka and Andhra.Farmers start the new agriculture season during this month as it falls during the peak monsoon season and most rivers overflow during this period. People celebrate this and pray to keep the rivers always filled so that they will have enough water for agriculture. This month includes the birthday of Sri Andal (one among 12 great Alwars of Sri Vaishnavism who wrote Tiruppaavai and is also considered as a manifestation of the mother Goddess) who was born on Pooram nakshtra during this month. The month is considered special and is dedicated to Shakthi worship.The Varalakshmi pooja observed by women falls in this month when they observe fast (Vratha) for the well being of the family.
Some believe that Lord Surya (Sun god) changes his direction from north to south in the Aadi month. The next six months from Aadi to Margazhi is symbolically the night time of the Devas (Dakshinayana punyakalam). Hence many auspicious events like marriage and house warming are not performed during the month. New ventures are not begun fearing failure to yield desired results. However,the real reason may be that such a practice was adopted just to help future generations focus on worship of Shakthi and not be distracted by such events. This may have also been done to focus all efforts on the new agrcultural season.Newly weds were not allowed to stay toegther and usually the bride would be sent back to her mother's home to avoid conception during this month which results in the new born arriving in April or May making it very difficult for both mother and the new born child, these being the hottest months in the year.However, over time the reasons have been forgotten and the month itself came to be considered inauspicious.
Fortunately, the tradition of Shakthi worship is still being followed with celebrations in all temples during this period.