Why does sf get fog

What exactly is fog? Technically, it is a field of water droplets suspended at or near the surface that significantly reduces visibility. In San Francisco, fog is most common during the summer due to a combination of environmental conditions that cause wind patterns and ocean currents in the North Pacific to play off one another. One of the first steps involves the northward migration of the Pacific High, a high-pressure weather pattern that strengthens and moves toward the coast in the spring and summer.

The high causes wind patterns to shift, which in turn affects the California Current, a major ocean current that flows from British Columbia south along the Pacific coast. As this happens, deeper, colder water rises up to replace it, a process called upwelling. Upwelling causes water temperatures in the Pacific to be frigid, but biologically productive. When sea breezes blow over this cold water, water vapor is forced to condense out of the air, forming advection fog.

A different type of fog— tule fog —forms in San Francisco during the winter due to a separate set of meteorological conditions. For reference, the city of Tampa, Florida clocks an average of clear days per year. The San Francisco fog is definitely a regular sight, but locals get their share of pleasant days, too. So how many days a year is San Francisco actually foggy? We know San Francisco enjoys about clear days.

Does that mean that the remaining days of the year are foggy? The City by the Bay can expect to experience fog about days a year. Summertime is the foggiest season in San Francisco. Remember, the fog is driven in part by high-temperature inland air. If you wish to avoid the fog, winter may be the best time to visit. The warmer summer months of June through August are the foggiest time in San Francisco. However, the foggiest overall month is probably June. As we mentioned earlier, the fog in San Francisco has earned its own moniker — it goes by Karl.

Naming the fog has helped to personify it, turning it from a dark and brooding presence to a sort of friendly, if damp, neighbor. But how on earth did Karl earn his name? A local San Franciscan saw this and ran with the idea to make a Twitter account for Karl. Much like his namesake, Karl the Fog is not malicious or bad. The fog comes on little cat feet. It sits looking over harbor and city on silent haunches and then moves on. San Francisco may be known for its foggy conditions, and rightly so: the city does have its fair share of foggy weather.

The natural meteorological and geographical conditions in the San Francisco area lend themselves to fog. List of Partners vendors. By Allison Serrell. Share Pin Email. Was this page helpful? Thanks for letting us know! Tell us why! Your Privacy Rights. To change or withdraw your consent choices for TripSavvy. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page.

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