Apparently, Krakow is famous for its fog.
After living here for nearly 7 months, and experiencing all four seasons (winter came to Krakow a few weeks ago with a 25 cm dump of snow that is still on the ground), I understand why. It can be foggy at any time of day - spring, summer, fall and winter.
Tonight my friends and I stepped out of the gym into complete fog. It is pretty, but not so much fun to drive through.