Why are summers so cold in San Francisco?

Off California, there is a cold buoyancy current from the deep sea.The Pacific Ocean is several thousand meters deep. Central and Southern California are in the area of influence of the subtropical high over Hawaii, which means that the trade winds generated by the high force are driving the seawater in southern California to the west, and is being replaced by the cold deep-sea water, because the American land mass prevents the influx of Atlantic water.

At the same time, the Kuro-Shio brings electricity from the Western Pacific to the canadian west coast, where the weather is mild for the latitude.This current then turns south and draws cold water from the Arctic to the south.

These two cold streams of water merge to create a coastal parallel California stream.The water off California is thus very cold, similar to before Chile and Peru, where a similar ocean stream is called Humboldtstrom. There is also a deep-sea ditch off the coast for particularly cold water.

The Pacific Ocean off California often has little more than 10 degrees, such as off San Francisco.Off San Diego on the border with Mexico, the sea is still barely warmer than 20 degrees, which is why you surf there in rubber suits. Even far into tropical areas on Baja California, the water of the west coast is unpleasantly cold.

When warm, subtropical and tropical air flows over such cold water, fog inevitably arises.This is then driven inland by the sea wind, because inland California there are high temperatures. It’s like a chimney effect. The fog feels cold, damp and clammy, and it often doesn’t go away on the coast all day. So it’s no surprise that San Francisco is bubbling at 14 degrees in June, like the foggy olten here in mid-November.

Santa Monica and Long Beach near Los Angeles aren’t much better off either.Foggy cloudy until noon, 20 degrees. And that in June! San Diego, meanwhile, experiences constant high fog days in the spring, and it sneesays against the mountains. If you drive over the 1800 m high mountain range you will find within a few km bone-dry desert heat and hardly any vegetation.

This continuous autumn weather can also be found at Guerrero Negro just on the turning circle, at the bottom of Baja.It is cool, foggy and humid, yet the area is one of the driest spots in North America. The Vizcaino Desert is a fog desert similar to the Atacama in South America.

Usually the weather character changes in midsummer, certainly in autumn, when rather eastern winds drive the cold fog soup back to the open Pacific.As these winds descend from the mountains, they warm up like a blow-dry. Then there are up to 40 degrees in San Francisco, and 45 degrees in Los Angeles. San Diego and Baja have it better, the mountains are lower and it doesn’t get so hot. But sunny all the time.

So autumn in and of itself is the best time for California – if the wildfires weren’t.Otherwise, the early spring is often not bad, if it is still too fresh for the sea wind.

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