We've had some seriously serious fog these past two days. It rolls in waves from the lake and creeps inland for 1/2 a mile or so. And it keeps temperatures low. I had an errand to run out in the western 'burbs. It was 88 degrees when I left the 'burbs. It was 55 degrees back in the city.
Downtown was the most dramatic, though, as the fog gets trapped in the building canyons. These were taken at 8:30 in the morning.