Fog comes from the condensation of water vapor in the air near the ground. It forms when the air cools to the dew-point temperature, the point at which water vapor condenses into tiny droplets suspended in the air, creating a visible cloud-like layer close to the surface. This typically happens when the ground loses heat overnight, cooling the air above it under certain conditions such as clear skies and light winds, often after rain increases moisture in the air. Fog needs high humidity, particles like dust or pollution for the water vapor to condense around, and the air temperature and dew point to be very close.
Fog is essentially a cloud touching the ground, formed similarly to clouds but at lower altitudes. Different types of fog can form based on environmental conditions, including radiation fog from ground cooling and advection fog when moist air moves over cooler surfaces.
Thus, fog originates from cooling moist air near the surface leading to water vapor condensation into tiny droplets suspended in the air.
