Do you know why deserts are formed' Deserts owe their origin to the lack of water in hot climates. Warm air over the land retains most of the available moisture. To add to this, the high evaporation rate turns the land into a desert. Also high mountains that lie across the path of the rain clouds and moist winds act as a shield. So most of the rain falls over the mountains before they reach these plains. Another reason is that some of the plains are so deep within the continent that the moisture-laden winds hardly ever reach them, turning them into deserts.