A wind gust is defined as a rapid fluctuation in wind speed, usually lasting less than 20 seconds. There must be a variation of at least 10 knots (12 mph) between the peaks and lulls of the wind speed to report a gust. Wind gusts tend to be higher in unstable situations when cold air moves over warmer ground or over water. Frequently, during outbreaks of cold air in the autumn or winter, wind gusts may exceed the average wind speed by 25 or 30 mph. During thunderstorms, rain-cooled air descending from a cumulonimbus cloud may generate gusts of 100 mph. Atlanta's airport often has gusts between 30 and 45mph during the time a cold front is moving through. During Tropical Storms or Hurricanes along the Georgia Coast winds affect areas inland too so that often causes gusts at the airport in Atlanta to between 50 and 65mph!
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