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.