Fog – Millions of Tiny Water Droplets

Fog droplets stay floating because they are so incredibly small, thinner than a human hair. Because they are so light, they have a very low “terminal velocity,” meaning they fall toward Earth extremely slowly, sometimes at just one centimeter per second. Even the slightest upward breeze or gentle air current is enough to push them back up and keep them suspended in the air. Fog forms in several ways, depending how the air cools or gains moisture. Radiation fog occurs on clear, calm nights as the ground cools the air above it, while advection fog happens when warm, moist air moves horizontally over a cold surface, like the ocean. In mountainous areas, valley fog settles in low points as heavy, cold air sinks, and upslope fog is created when wind pushes moisture up a hillside. Steam fog looks like smoke rising from water when cold air passes over warmer lakes. In extreme cold, freezing fog creates icy coatings on surfaces, while ice fog turns droplets directly into tiny floating crystals.

Source: Scientific American (https://www.scientificamerican.com/article/why-do-clouds-float-when/)