“Sea Breeze” isn’t just the name of a thousand beach motels.
The breeze coming in from the sea is a real phenomenon that makes the shore cooler than it is inland at least in the afternoon, which is when people most want to cool off anyway.
In the daytime, cool breezes almost invariably blow in from the ocean toward the land, rather than the other way around. They begin several hours after sunrise, reach their peak by mid-afternoon, and die out toward evening.
Here’s how it happens.
Starting in the morning, the sun beats down on both land and sea. But the sea isn’t noticeably warmed by the sunshine because it is so cold and vast that it has an inexhaustible appetite for heat energy, slurping it up with nary a degree’s rise in temperature.
The land, on the other hand, is substantially warmed up by the sun’s rays. Soil, plant leaves, buildings, roads, and so on are relatively easy to heat. (Techspeak: they have low heat capacities, compared with water.)
As the land warms up, it warms the air above it, which expands and rises. The cooler, denser air that is sitting over the water then rolls in underneath it, sweeping over the beach and cooling bathers.
It’s not just that the ocean breeze is cool. Even if it weren’t, it would still help to cool the sweltering hordes by evaporating perspiration.