A cloud is made up mainly of water. When hot air rises from the land or the sea, it carries water vapour
with it. Because the atmosphere usually gets colder with height, and cold air can hold less vapour
than warm air, the vapor eventually condenses in the form of water droplets or ice crystals around
particles of dust to form a cloud. If it continues to cool further, the cloud will become denser until the
atmosphere is no longer able to hold the moisture and rain, hail or snow will fall. The general rule is that
the deeper a cloud is relative to the deeper a cloud is relative to the height of its base above the sea or
ground, the more heavily it will rain, hail or snow, so thin, high clouds produce no rain, while thunder
storms produce a great deal.