A monsoon is a seasonal period characterized by a prevailing wind often accompanied by heavy rains. Monsoons are experienced in some regions of south Asia on Earth.
The planet Hanoran II experienced a monsoon season. In 2375, Jean-Luc Picard was frustrated about needing to delay an archaeological expedition to the planet, as the mission would then be moved to the middle of their monsoon season. (Star Trek: Insurrection)
In 2372, Harry Kim described the storms that gathered around the USS Voyager as it attempted to land on the planet of the Sky Spirits as monsoon conditions. (VOY: "Tattoo")