Ashdhi-Beej

Just as we use kites in the winter / spring season to predict the weather, during the pre-monsoon, there is a small festival called Ashadhi-beej to predict the monsoon.
During Ashadhi-beej, they check the moisture in the atmosphere to help predict which crop would do best in coming monsoon.

Ashadhi-beej is calculated at two main places in India.
1) VishvaNath temple in Varanasi, UP
2) Mulesh Mahadev in Umreth, Gujarat

Sample seeds of crops to be planted are weighed and left in the temple's inner sanctum overnight in an earthen pot.
Next morning, they are weiged again.

Percentage gain in weight is an indication of good crop of that seed.
If there is a loss in weight, crop of that seed is likely to be bad.

They also check the weight of "soil" to see if the coming season will increase the population or reduce it.

Moisture in the air makes the seed / soil gain weight. If the pre-monsoon air has a lot of moisture in it, that is a fairly good indication that the season will be well.