Annual rainfall refers to the total amount of precipitation, primarily in the form of rain, that an area receives over a year. It is typically measured in millimetres (mm) or inches. The annual rainfall is a key indicator of a region’s climate and directly influences ecosystems, agriculture, water resources, and human activities. Rainfall patterns are often dictated by geographical factors such as latitude, elevation, proximity to bodies of water, and atmospheric conditions, including the movement of weather systems and monsoons. Different regions can experience vastly different annual rainfall amounts—arid areas may receive only a few millimetres, while tropical rainforests can receive thousands of millimetres annually. Monitoring annual rainfall is crucial for managing water supplies, predicting agricultural yields, and planning infrastructure, especially in regions prone to floods or droughts, where variability in precipitation can have significant social and economic impacts.