What makes the wind pick up so quickly when there's a thunderstorm coming--even if there was not much wind before that?
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Thunderstorms generate strong updrafts and downdrafts of air.  As the storm builds, air from the surface is drawn up into the storm.  This inflow creates a rush of air toward the storm resulting in a strong wind at the surface.  This air is drawn up to tens of thousands of feet where it is very cold, lower than -30 degrees F.  As the air gets colder, it becomes more dense.  This column of cold air starts to descend and when it reaches the ground, a gust of wind blows outward from this descending shaft of air.
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In its early and middle stages a thunderstorm is a column of rising air and that creates wind.  In the latter stages a thunderstorm is mostly descending air.
      