WADR that is just BULL. Have you ever been to a desert? If anything, there may be more flies per square inch in a desert such as Arizona, than there are in a wet climate like Florida. And in the spring, So. Calif IS wet, and don't forget it.
If anything or anybody shits in the open in a desert, a fly lands within 10 min, if not 10 sec, let me tell you. Trash, including fast food and ice cream containers, littered this area.
Would somebody who lives in one of the three driest major cities in the USA, Las Vegas, Albuquerque, and El Paso, please step in and tell this poster the truth about flies!
San Diego is much damper and more temperate.
I doubt this information will help, but we lived in Boulder City, NV. for 6 yrs.(just south of Las Vegas) The flies were horrible. Dry, hot, wet, or cool. We now live in the Dallas area. Mostly hot and humid. We live across the street from a horse pasture. The fly problem is minute compared to NV.