Monsoon is actually a word derived from the Arabic word 'mausim' which means seasonal reversal of winds.And we know India has a monsoon type of climate so by June the winds around equator get deflected due to the force made due to the rotation of the earth known as Coriolis force and they first arrive to the mainland of India in June 1 at Tiruvananthapuram . So it brings heavy rain to India as it blows from sea to land.