<P> Various atmospheric conditions influence the monsoon winds . The first condition is the differential heating and cooling of land and water . This creates low pressure on the landmass, while high pressure is created over the seas during daytime, but is reversed during the night time . </P> <P> The second condition is the shift in the position of Inter-Tropical Convergence Zone (ITCZ). In summer, the equatorial trough normally positioned about 5 ° N of the equator moves over the Ganga plain creating a monsoon trough during the monsoon season . </P> <P> The third condition is the presence of the high - pressure area that develops east of Madagascar . It is approximately at 20 ° S over the Indian Ocean . The intensity and position of this high - pressure area affects the Indian Monsoon . </P> <P> The fourth condition develops during the summer . The Tibetan Plateau gets intensely heated resulting in strong vertical air currents and high pressure over the plateau about 9 km above sea level . The fifth condition develops during the summer due to the movement of the westerly jet streams to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian Peninsula . </P>

When do monsoon rains come to mainland southeast asia