A season of high temperatures, high winds, and high moisture, resulting in potentially deadly weather. The term "monsoon" comes from the Arabic "mausim" meaning "season" or "wind shift". It is this change in wind direction that causes stormy conditions, including wind, dust, and rain.
Prior to 2008 the Arizona monsoon was defined as beginning after the third consecutive day of dew points above 55°F. On average this occurred around July 7 with the monsoon continuing for the next two months. Starting in 2008 the National Weather Service has defined the Arizona monsoon as beginning on June 15 and ending on September 30.
During monsoon we get about 2-1/2" of rain, about 1/3 of our yearly rainfall. However the monsoon varies from year to year in intensity.