“Encyclopedia of Deserts” by Michael A. Mares, Oklahoma Museum of Natural History (Norman, Okla.) is a good source of information on dew formation in the desert.
Here’s a quote from page 177:
“It is not exactly known how much dew forms on plants in desert areas, although it rage from 10 millimeters in cold climates to as much as 75 millimeters per year in subhumid warm areas. In some desert areas, especially semiarid and Mediterranean habitats, dew may contribute a significant percentage of the total precipitation that is available in the area during the year for plants and animals.”