Why do tropical wet and dry climates have a dry period?

Tropical wet and dry climates, also known as savanna climates, experience a distinct dry period due to the seasonal movement of the Intertropical Convergence Zone (ITCZ). During the wet season, the ITCZ brings moist air and rainfall, while in the dry season, it shifts away, leading to reduced precipitation. This seasonal variation is influenced by the subtropical high-pressure systems that develop, causing dry conditions. The result is a climate characterized by a clear contrast between wet and dry seasons.