High Clouds

Middle Clouds

Low Clouds

Vertical Clouds


Fog is a collection of liquid water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog is distinguished from mist only by its density, as expressed in the resulting decrease invisibility: Fog reduces visibility to less than 1 km (5/8 statute mile), whereas mist reduces visibility to no less than 1 km. Fog forms when the difference between temperature and dew point is generally less than 2.5 °C or 4 °F.