When it's misty out, there's a heavy fog. The air is thick with moisture, and there's just barely a light rain.
When the air is foggy or hazy, you've got a misty situation. It isn't easy to see through misty weather, which happens most often in the morning because of moisture in the air. Your eyes can get misty too, when you're about to cry because you're sad or just have allergies. In fact, people who are embarrassed about crying will often joke, "It's getting misty in here."
