The monsoons usually happen due to the differential heating of land and water. You probably know that land heats faster than water. This change in heating leads to a difference in pressures, which in turn leads to currents. Thus, the changes in pressure conditions also affect the monsoons. The differential heating and cooling of land and water create a low pressure on the landmass of India and high pressure on the Indian Ocean area. Shifting of ITCZ: This leads to the shifting of the position of the Inter-Tropical Convergence Zone (ITCZ) in summer, over the Ganga plain