Must not have worked on a row crop farm much, either! :) These things need some dry, loose ground so they can pick up dirt/dust/leaves (sheet metal?) that make them visible. But they can also form over water, they are then called 'water spouts'. Here are a couple of links that explain small but strong vertical winds/updrafts; no clouds needed.<weatherquestions.com (http://www.weatherquestions.com/What_are_dust_devils.htm)>
<Wikipedia (https://en.wikipedia.org/wiki/Dust_devil)>
Edited to hopefully sound less authoritative and condescending! My bad [banghead]
Great story "Bull", now I know how you got that name...
BTW, are you sure you weren't knocked to the concrete back in that college 'encounter'? Jis' sayin'
(http://i1327.photobucket.com/albums/u666/xAirbusDriver/tease_zpsrq5td6hw.gif)