According to varahamihira formation of clouds takes place 195 days before their birth Cloud groups:

1. Abartak : received in certain places in that year
2. Sambartak: received in all of the country
3. Pushkara: the quantity of will be very less
4. Drona: that year will receive abundant rain water

Among this Nimbostratus and Cumulonimbus gives rainfall to the earth.