The word "monsoon" is derived from the Arabic word "mausim" which means "wind-shift". During the winter, the primary wind flow in Arizona is from the west or northwest. In the summer the winds shift. The moisture streams from the Pacific Ocean and the Gulf of Mexico, along with this wind shift and the heat of the summer days, produces a significant change in moisture conditions.
The onset of the Arizona monsoon is said to occur when there are 3 or more consecutive days of dew points averaging 55°F" or higher. This period is characterized by high humidity and periodic monsoon thunderstorms.
