The Indian summer monsoon climate is crucial for the region's agriculture and economy. Scientists have been trying to predict its year-to-year variations, but it's proven to be very challenging. The monsoon is driven by the migration of a rain band and a circulation pattern associated with it. While the classical model explains the wind reversal, it fails to account for the monsoon's onset and maintenance. The key to understanding the monsoon lies in the change of temperature gradients in the atmosphere, which triggers the monsoon's onset and progression.