Changing weather patterns brought heavy fog to the San Carlos Caltrain station on Thursday, Feb. 26, 2026.

The National Weather Service issued and then extended a dense fog advisory on Thursday for parts of the Bay Area, including the San Francisco bayshore, the North Bay and the Salinas Valley, as developing high pressure in the area this week helped usher in the weather phenomenon.

The heavy fog is expected to last through at least Thursday morning and resulted in low visibility for much of the region at the start of the morning commute. The San Francisco bayshore fog advisory was expected to expire at 9 a.m., but low cloud cover could remain.

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“Mid- to high level cloud cover streams over the Bay Area and Central Coast, below which low stratus and fog is developing in the wake of the widespread light rainfall from the last couple of days,” the National Weather Service said in its forecast discussion for Thursday.

Roger Gass, a meteorologist at the weather service, said different weather dynamics could have turned the heavy fog into rainfall. Instead, the high pressure is helping keep that moisture suspended in the air. 

“That’s creating the perfect storm to have this dense fog,” he explained.

Heavy fog and clouds could be seen from space on Thursday, Feb. 26, 2026.

The thick fog bank, which could be seen from a National Oceanic and Atmospheric Administration satellite on Thursday morning, is expected to dissipate over the course of the day, although much of the region is expected to be cloudy throughout Thursday.

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“We could still have additional fog tonight before the next storm system arrives,” Gass said. 

Don't let Google decide who you trust.

The high pressure is expected to keep out any major precipitation to the area until at least Monday, when light showers are possible in the Bay Area, Gass said. 

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