Monsoons occur because of seasonal shifts in wind patterns; they create wet and dry seasons in areas where prevailing winds change throughout the course of the year, creating stagnant wind and weather patterns. Monsoons, like other weather patterns, draw influence from temperature and atmospheric conditions. Their formation takes long periods of time, as monsoons gradually accrue moisture and density, developing large clouds that produce large volumes of rainfall.
Throughout the year, approximately one quarter of the globe experiences monsoons. Monsoons exist in two primary forms: summer and winter monsoons. During the summer, most land areas generate more heat than ocean waters. The warm air over land draws air inward from the ocean, inviting the connection and solidification of molecules. Warm, rising air over land areas eventually creates large clouds. These clouds collect water moisture and water vapor. Eventually, they grow to large sizes, capable of producing steady rainfall. These heavy, moisture-laden clouds remain over certain areas of land, releasing rain between the months of April and September.
While winds during the summer keep monsoon clouds in place, seasonal shifts in wind patterns for the winter season drive the clouds away and prevent formation of new clouds. This creates the characteristic dry air and clear skies of winter monsoons. Although monsoons change seasonally, other weather patterns might affect their patterns. A weak El Nino, for instance, creates more rain during summer monsoons and triggers atmospheric instability, resulting in unusually turbulent or calm conditions.