Fog typically forms at what visibility range?

Fog is defined as a cloud that touches the ground, and it significantly impacts visibility. Typically, fog forms when the visibility is reduced to 1000 meters or less. This reduced visibility occurs when moisture in the air condenses into tiny water droplets, creating the dense, low-lying cloud layer we identify as fog.

Fog formation is influenced by several factors, including moisture content, temperature, and atmospheric pressure. When these conditions are favorable, particularly in cool and calm situations, fog can quickly develop, leading to visibility dropping below 1000 meters. This threshold is critical for pilots and drivers alike, as it indicates a significant reduction in visibility that can affect navigation and safety.

While visibility can be reduced to lower levels like 1500 meters, 3000 meters, or even 5000 meters in different conditions such as haze or mist, these do not typically meet the criteria for fog, which specifically requires reduced visibility to under 1000 meters. Thus, the choice that states fog typically forms at visibility below 1000 meters is the accurate one.