A number of years ago I spent a year on a ship going from LA to San Francisco and that was a pretty common sight.
We berthed at Richmond, and it would be bright and sunny, yet an hour after leaving, rounding Angel Island, you would hit the solid bank of fog until out past the pilot station.
Craziest thing I saw, (only just!) was going under the Golden gate, and having kite surfers coming towards the ship at a rapid rate of knots, seeing this massive wall of steel in front of them, and then having to peel away at the last minute!
we only picked them up on the radar at the last minute, and could only just see them as they got to within about 50 metres of the ship!
How we never minced them up with the prop, I will never know.
We tend to not sail if the fog is too bad now, but still get caught out in it on occasion.