Fog

Fog is a visible aggregate of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface, reducing horizontal visibility to less than 1,000 meters. It is one of the most common causes of flight delays, diversions, and airport closures worldwide.

• Radiation fog: Forms on clear, calm nights as the ground cools
• Advection fog: Warm, moist air moves over a cold surface
• Frontal fog: Forms near weather fronts, especially warm fronts
• Upslope fog: Moist air forced up terrain slopes
• When temperature/dew point spread ≤ 2°C with light winds, fog is likely