What is fog, and how does it form?

Fog is identified as a cloud that forms at ground level when the air cools to its dew point. This process involves the cooling of air to a temperature at which it can no longer hold all its moisture in the form of vapor, resulting in condensation. As the air cools, tiny water droplets form, creating the dense visibility-reducing effect associated with fog.

In atmospheric conditions, this typically happens during nighttime or early morning when temperatures drop. It can also occur in various locations and under different climatic conditions, not confined to specific seasons or temperatures. Understanding this formation process is crucial in meteorology as fog can have significant impacts on visibility, weather patterns, and local environments.

Other options either describe processes that lead to cloud formation at higher altitudes, mist formation through evaporation (which is distinct from fog), or wrongly assert that fog only occurs during winter, which is not the case as fog can form in varying weather conditions throughout the year.