Page "Dust devil" Paragraph 23

On Earth, most dust devils are very small and weak, often less than 3 feet ( 0. 9 m ) in diameter with maximum winds averaging about 45 miles per hour ( 70 km / h ), and they often dissipate less than a minute after forming.

On rare occasions, a dust devil can grow very large and intense, sometimes reaching a diameter of up to 300 feet ( 90 m ) with winds in excess of 60 mph ( 100 km / h ) and can last for upwards of 20 minutes before dissipating.