Multiply the Saka Year by 8 and divide the sum by 9. The remainder is megha (rain) index. The index with names of megha areas are as follows.
- Avarta,
- savarta,
- pushkar,
- droan,
- kal,
- nil,
- varun,
- vayu and
- tamas.
There will be good rains when it is Avarta, pushkar, varun and vayu
Similarly, add 2 to saka year and divide by 12. The remainder gives naga index. The indix and names of naga are as follows
Subudha, nandsari, karkot, prithusrva, vasuki, nakshatra, kambal, as avatar, hemmali, narendra, vajradranksatra and vrisha.
The Sun’s entrance in rashi mesha indicates lunar nakshatra and position of megha. Vrishti occurs when the Sun’s journey is from Mrigasira to Hasta nakshatra.
The union of planets Budha and Shukra, Budha and Guru, Guru and Shukra indicate rain. The greater the number of planets nearer the sun, the more are the chances of rain.
There are nine nakshataras (out of 27) in addition to Rohini, which are more favorable for rains. They are Mrigasira, Ardra, Punarvasu, Pushya, Aslesha, Magha, Purva Phalguni, Uttara Phalguni and Hasta. The rains will occur on the day when any of the above nakshatras starts.
The day when moon enters Purvashadha nakshatra, after the first day of Shukla Maragsirasa, is called Meghagarbha day. Around 195 days after this, meghas will deliver rains as per Hindu astrology.