Have you ever gone to the beach twice in one weekend and the water temperature was drastically different from one day to the other?
I used to work as an ocean lifeguard and I would witness this fluctuation in temperature all the time. I vividly remember measuring the water temperature at 70 degrees one afternoon and waking up the next morning to a 58 degree swim! Less than 24 hours and the water temperature had dropped 12 degrees. Wow!
It all has to do with the wind. In summer, an ocean breeze (NE, E, SE wind) brings in warm surface water heated by the sun to the coastline. This direction of wind will bring warmer water temperatures even though the air feels cooler.
However, winds blowing from inland (SW, W, NW wind) push the warm surface water away out to sea. Cold water then rises up from beneath the surface to replace the water that was pushed away. This process is known as “upwelling” and occurs all the time along our coastline. This colder water from beneath is rich in nutrients and nourishes our coastline, creating high biological productivity.
For a beachgoer's purpose it's a balance of wind direction that can make for a beautiful day in the water and on the sand. So next time you plan a day at the beach keep an eye out to see which way that flag is blowing!