Fog

Fog means that the air is so saturated with small water droplets that the visibility is less than 1 km. If the visibility is between 1 km and 1 mile, you instead speak of haze. If the fog consists of ice crystals, it is called an ice fog. There is no difference in principle between fog and clouds, only that clouds do not reach the ground.

In order for haze and fog to form, the air needs to be very humid. In most cases, the temperature also drops in connection with the formation of haze and fog. When the temperature drops, water vapor condenses into water droplets, if the air is humid enough, forming fog and haze.