The fog was dense in some spots, patchy in others, as temperatures hovered in the mid-40s and the humidity pushed past 90%.
In Teaneck, a thin blanket hovered over Votee Park after dark. Some areas got worse -- by much -- through the overnight hours.
It was expected to continue into the morning as temperatures began a push past 60 degrees -- more than 10 degrees above normal for this time of year. A National Weather Service fog advisory remained in effect through 9 a.m. for most of northeast New Jersey, as well as the lower Hudson Valley, Long Island and southern Connecticut.
Radiation fog, as it's called, is most common in the fall, "when nights get longer, air masses begin to cool, and land and water surfaces that have warmed up during the summer are still evaporating a lot of water into the atmosphere," according to the Glossary of Meteorology from the American Meteorological Society.
"Specifically, fog reduces visibility below 1 kilometer (or 0.62 miles)," the society said.
There could be more in store: Warm weather was expected Saturday and Sunday -- with temperatures ranging in the low-to-mid-50s.
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