In desert country, where they’re most common, dust devils are about the same color as the ground below, so they may be hard to see from overhead.   But when it’s sunny you can sometimes spot the shadow of a dust column, visible as a faint gray oval moving downwind.   It will be easiest to see when the sun is high (the very time when devils are most numerous), for light is then falling further through the dust column, concentrating and darkening its shadow.        There can also be an even subtler indication:  if you’re looking down on a nearby devil, dust suspended in the air will make minute terrain features appear blurry.   Watch closely any small area that seems less sharply visible, to see if that blurriness migrates across the surface.   With either of these signs, you have two valuable pieces of information:  the dust devil’s surface location and direction of drift.   Also, two devils imply a line of lift, and three in a row nearly confirm it.