Dust devils result from when superheated
air near the ground rises up to meet with the cooler air aloft resulting in a weak
vortex which superficially resembles a
tornado. They form usually on hot
sunny days with a weak
breeze.
Dust devils are not associated with thunderstorms, and they can rotate clockwise or counterclockwise, regardless of if they are in the northern or sothern hemisphere. Some extreme cases have reported dust devils with winds in excess of 50 miles per hour and rising in size to more than 5000 feet above the ground, though such occurrences are very rare. Most dust devils are very small and only kick up leaves and dust across an open field.