These web pages illustrate and explain the classification of cloud types, so that observers are able to report the types of cloud present.

Classification is based on ten main groups of clouds, which are divided into low, medium and high levels depending on the part of the atmosphere in which they are usually found. A code figure designated C_L, C_M or C_H is used to describe the clouds of each level. When there is more than one type of cloud present at any level, an order of priority has been arranged by the World Meteorological Organization (WMO) to determine which code figures should be used.

A separate section is devoted to the clouds at each level. A pictorial guide at the beginning of each section shows the priority of coding. To find the correct code figure for any cloud level, follow the relevant pictorial guide.

In some meteorological messages, clouds are identified according to the ten main groups. A code figure, designated C, is used. All references to C code figures are shown as Cn or C=n (e.g. C9 or C=9).

Worldwide, the height of cloud base is still reported in feet (ft).

Acknowledgement
The Met Office is indebted to the photographers, whose names appear against the individual photographs, for permission to reproduce their work on these web pages.