One of the name of Lord Shiva is `Soma` or `Saha Uma`. Shiva is also called Lord Someshvara as he wears the Soma or the moon crescent on the mottled hair. On the Somavara day or Monday, this Vrata is observed to remember Lord Shiva.

All Mondays can be observed as Vrata but there are special Mondays when the observation of this Vrata is emphasized like the Shravana Somvar and the Karthikai Somavar. According to Skanda Purana the Vrata is observed on the month of Karthikai(mid November to mid December).

There is a certain way of observing the Vrata. The devotee gets up early in the morning and meditates on Supreme Lord Shiva. The devotee first takes bath and perform the morning twilight salutation first. He /she prays to the graceful Lord Shiva and also worship the divine couple Parvati and Maheshvara. The follower of Lord Shiva offer the lord feast but observer himself eats only one time food that day. If one is unable to perform the
worship at home then can go to temple to salute uma and Maheshvara. The Lord is anointed with Bilva leaves and also offered nice sweet foods like Panchyaamritam and other pleasant substances. The food is shared among all kind-hearted devotees after the puja is over. One might keep fast completely according to his/her wish.

One who observes the Vrata would get to enjoy many earthly pleasures as well as finally would reach the abode of Lord Shiva, Kailasham. The moon observed this Vrata to get his `moonness`. He saluted lord Gauri-Shankara and requested that this Vrata should be called Soma Vara Vrata as moon`s other name is Soma as well as the couple of God Shiva and Uma is also known as `Soma`.Whoever follows the Vrata get the Lord`s boon and all their wishes are materialized.

There is also a story related to Soma Vara Vrata. Long ago a princess, named as Simanthini used to observe the Vrata regularly. Then two young boys cunningly simulated as a married couple. The princess worshipped them with true belief. After that the young boys were really converted into male and female couple.

The shiva-sakthi on observing this Vrata regularly blesses one.