Winds are caused as a result of differences in temperature between the
various layers of the atmosphere. A certain amount of air becomes heated
and rises, and as explained before, expands. As the air expands, it
becomes lighter, and because it is light it goes upward toward higher
regions. It also flows from hot to cold countries. A good illustration
of this is the sea breezes. If you have lived around the seashore in the
summer time, you will have observed that during the hot part of the day
the winds generally blow from the sea toward the land. At night the
direction of the wind is reversed, that is, it blows from the land to
the sea. Why? Because the land during the day retains its heat, while
the water diffuses it. What is the result? The air on the land expands,
becomes light. The air over the water being cool, it does not expand,
and the result is that it presses toward the land. At night the land
loses its heat more rapidly than the water, so that it is not long
before the land is cooler than the water, and when this happens, the air
over the land, which has become cooler, presses seaward.