Valley fog is a type of fog that forms in low-lying areas, typically during the night and early morning. It occurs when the air cools and moisture condenses, creating a thick layer of fog that can reduce visibility significantly. This phenomenon is most common in valleys surrounded by hills or mountains, where cold air settles. The presence of valley fog is influenced by factors such as temperature, humidity, and wind patterns. It often dissipates as the sun rises and warms the air, leading to clearer conditions. This fog can create beautiful landscapes but may also pose challenges for drivers and outdoor activities.