You may not live in an area where you experience Monsoon Season so here's a little brush up on what it is and what it looks like.
An explanation I found online:
During the monsoon, or summer thunderstorm season, Arizona experiences more severe weather than many other states. On rare occasion, a severe storm may spawn a tornado. More often, high winds, dust and severe downpours resulting in flash floods are common monsoon occurrences.Here is a video of a 5 mile wide, 70mph dust storm that came in earlier this week:
Here's a time lapse of the same storm on July 5th 2011:
The Phoenix Haboob of July 5th, 2011 from Mike Olbinski on Vimeo.
Freaky, right? Scary too.