Himalayas acted on the monsoon in two ways. The Tibetan plateau, heated up during summer and thereby established an atmospheric circulation that was conducive for the monsoon. The vast mountain range also acted as a tall barrier, preventing cold, dry air in the northern latitudes from entering the subcontinent and subduing the warm, moisture-laden winds from the oceans that drive the monsoon.
Tibet gets heated in summer and is 2°C to 3°C warmer than the air over the adjoining regions. Because the Tibet Plateau is a source of heat for the atmosphere, it generates an area of rising air (convergence)(intense low pressure cell).
The Himalayas have a profound effect on the climate of the Indian subcontinent and the Tibetan Plateau. They prevent frigid, dry winds from blowing south into the subcontinent, which keeps South Asia much warmer than corresponding temperate regions in the other continents.