SAN DIEGO — On a vivid summer day in California, locals and tourists pack the beach, setting upwards on the sand and making sure to use lotion or the shade of an umbrella to protect from the sun's powerful rays.

Simply on that same embankment, it'southward not uncommon to encounter kids shivering as they run out of the water, or a surfer wearing a partial wetsuit every bit they jog out for a session.

California's ocean water is pretty cold, fifty-fifty in the summer, and it oftentimes catches visitors off-guard. What causes this phenomenon, and why practise water temperatures on the W Coast differ and so much from the ocean at a embankment in say, Florida?

Experts say two key factors chill the ocean even when the sun is shining: The common cold California Current, which flows south along the coast from the Gulf of Alaska, and a concept called "upwelling."

In a phone interview this calendar week, San Diego-based meteorologist Miguel Miller, who works for the National Weather Service, helped explain the ii forces.

Incoming from Alaska

Miller describes the California Electric current as a "river of cool air that'south transporting Alaskan h2o downward to California."

This basic map demonstrates how body of water currents create a northerly air current on the West Coast of the U.S., and a southerly air current in the Eastward. (Photo: National Atmospheric condition Service)

The air is driven, in part, past high pressure that sets up over the Eastern Pacific for long portions of the year. Scientists accept found that air moves around loftier force per unit area in a clockwise direction, which results in air current that flows from north to southward off the W Coast of the U.S.

Miller says the breeze is typically light, but information technology's consistent. Equally the moving air comes into contact with the Pacific Bounding main'southward surface, information technology pulls the h2o along in the same direction.

That sends the frigid waters of Alaska downwards past Washington, Oregon and so California en road to Mexico. If you've swam or surfed at a vacation spot in western Baja California, similar Ensenada or Rosarito, you know the h2o's dank there, too.

Swapping warm water for cold

Understanding the California Electric current can help a shivering swimmer grasp the second cistron at play here: upwelling. Miller personally credits this phenomenon for chilling our embankment day even more than the current.

Upwelling occurs when winds push aside the peak layer of ocean water — which is warmer from sitting directly in the sun. The water getting shoved away creates a vacuum that has to be filled with something, so colder water rises from the depths to the surface.

The same strong winds driving the California Current contribute to frequent upwelling at the coast in California. As air moves south, the World's rotation creates rightward force per unit area, pulling the air current and water abroad from the coast. This phenomenon is chosen the "Coriolis consequence." It moves objects correct of their intended path in the Northern Hemisphere and left in the Southern Hemisphere.

Meteorological terms aside, the terminate upshot is pretty straightforward: Warmer water at the surface keeps getting swapped for common cold water from below, and that ways you'll be bundling up subsequently a swim on your beach day.

Aforementioned breadth, unlike temps

The E Coast doesn't have the same atmospheric condition that contribute to our dank ocean temperatures. The warm Gulf Stream current flows from southward to north, bringing warm waters from the Gulf of Mexico and Caribbean Sea up past Florida and along the coast.

That warm channel isn't disrupted by the same degree of upwelling, either, letting those who have a dip in the Atlantic Bounding main in the eastern U.S. enjoy generally warmer temperatures.

From declension-to-coast, swimmers on the same latitude can see differences of five or 10 degrees — or even more.

For instance: San Diego'south average September water temperature is most 67 degrees. But follow the aforementioned line of latitude (32.7 Due north) to Charleston, S Carolina, and the average water temperature that month is around 82 degrees, according to the Fleet Science Center.

While this tendency generally remains true, Miller says the conditions influencing water temperatures are non ironclad. Tempest systems and any number of other forces can influence the weather condition on both coasts.

Sometimes upwelling is reversed entirely off the Due west Coast, for example, leading to unseasonably warm water temps in that location.

Mostly speaking, though, visitors should plan to cool off in the h2o and warm up on the sand when they come to California — even during summer. Tourists, yous've been warned.

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