Why do winds usually dinimish around 6 p.m.?

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Dear Tom,
In the summer, I find that the wind almost always dies around 6 p.m. or a little later. Why does this occur?
— Jenny Mack, Highland, Ind.
Dear Jenny,
Daytime winds diminish to calm by sunset all through the year, not just during the summer. It does not happen during stormy weather, when other factors keep winds blowing at night, but when fair days draw to a close, brisk daytime winds calm out.
This happens because the ground begins to cool when it is no longer receiving heat from sunlight, and the air above it cools also. Wind continues to blow a few hundred feet above the ground, however, and it continues to do so all through the night.
When the next morning’s sunshine heats the ground again, the wind aloft mixes down to the surface, and ground-level winds start to blow once again

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