"Monsoon." The word evokes images of the endless summer rains of South and East Asia...But in the American Desert Southwest, 'monsoon' means scattered but intense thunderstorms from late June through September. The hottest part of the year can also be the most dramatic.
From mid to late summer, moisture seeps up from Mexico; massive towers of condensation build all day until the storms unleash lightning and curtains of rain in the afternoon and evening. Find a hillside or a canyon's edge and enjoy the display. Just don't get caught in the open if a storm heads your way; lightning strikes and flash floods are very real threats.
(This scene shows a cluster of storms moving over the Tucson basin, taken from the Babad Do'ag Lookout on the Catalina Highway in the Santa Catalina Mountains.)