Before the sun came up, it was all dark with shadows casted down from the street lights. Once the sun rose, visibility was still low.
A Dense Fog Advisory was issued for many parts of the Bay Area until 11 a.m.
Video showed parts of downtown San Francisco could not be seen from a distance. You couldn't see the pillars of the Bay Bridge either.
The airports felt the worst of it.
If you landed at San Francisco International Airport, you needed a sign to tell you.
MORE: Rare heavy fog event delayed dozens of flights at Oakland International Airport
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"The fog was pretty thick, and when we entered the fog, it was pretty dark as if we entered a rain cloud. Made you wonder, is it raining? because you really couldn't tell," said Carlton, traveling from Boston.
The mid-morning at SFO saw passengers frequently checking signs to see if their flights were still on time. Just like Oakland on Monday, planes could not safely land or take off.
"The pilot mentioned the fog before we landed. What did he say? I have never heard a pilot talk about the fog, and he said it was very heavy," said Larry O'Rourke, traveling from Washington D.C.
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Nearly 50 flights were delayed and four were canceled.
A travel nightmare for early morning passengers.
Some say they rarely have seen it this bad.
"Flying into London was the only other time I had seen it like that where you were in the fog until you hit the runway," Carlton said.
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