Clouds are vertically divided into three levels: low, middle, and high. Each level is defined by the range of levels at which each type of clouds typically appears.
| Level | Polar Region | Temperate Region | Tropical Region | 
| High Clouds | 10,000-25,000 ft (3-8 km)
 | 16,500-40,000 ft (5-13 km)
 | 20,000-60,000 ft (6-18 km)
 | 
| Middle Clouds | 6,500-13,000 ft (2-4 km)
 | 6,500-23,000 ft (2-7 km)
 | 6,500-25,000 ft (2-8 km)
 | 
| Low Clouds | Surface-6,500 ft (0-2 km)
 | Surface-6,500 ft (0-2 km)
 | Surface-6,500 ft (0-2 km)
 | 
 The types of clouds are:
High clouds: Cirrus (Ci), Cirrocumulus  (Cc), and Cirrostratus (Cs). They are typically thin and white in appearance, but can appear in a magnificent array of colors when the sun is low on the horizon.
Middle clouds: Altocumulus (Ac), Altostratus (As).  They are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are low enough.
 Low clouds: Cumulus (Cu), Stratocumulus (Sc), Stratus (St), and Cumulonimbus (Cb) are low clouds composed of water droplets.