Why do some tropical regions have rainy seasons and a dry season?

Tropical regions experience rainy and dry seasons primarily due to the movement of the Intertropical Convergence Zone (ITCZ), which is where trade winds from the Northern and Southern Hemispheres meet. During certain times of the year, the ITCZ shifts, bringing moist air and resulting in heavy rainfall. Conversely, when the ITCZ moves away, dry air predominates, leading to a dry season. Additionally, local geographical features, such as mountains and ocean currents, can influence rainfall patterns in these regions.