Why does wind blow?
The short answer
Wind forms when uneven heating creates pressure differences and air moves from higher pressure toward lower pressure.
How it works
Warm air expands and rises, leaving lower pressure near the surface. Cooler, denser air creates higher pressure. Air flows to reduce the difference, while Earth's rotation also changes its direction.
A familiar example
Near the coast, the land and sea heat and cool at different rates, so the wind can reverse between day and night.