Contrary to popular belief, clouds aren’t made of cotton candy, but of a conglomerate of cool water vapor that has condensed due to the temperature at higher altitudes. The altitude at which the condensation happens depends on the humidity and the rate at which temperature drops with elevation. Additionally, different weather conditions greatly affect the ability of cloud formation, understandably, with temperature playing a key role. This helps explain why you will often see very few clouds in summer, but seemingly a lot more in winter.
Meteorological conditions also determine the type of clouds, because, as you may have noticed, not all cloud formations are the same! Here are some of the most common types of clouds you may encounter on a day to day basis.
Clouds which form at very high altitude are called cirrus clouds, and are known to reach heights of 6,000 meters (10,000 feet). Usually thin, these clouds do not produce rain and are considered to indicate fair weather.
Mid-level formations, found between 2,000 meters and 6,000 meters (6,500 – 10,000 feet) sport the prefix ‘alto-’, with their shape determining the rest of the name — for example, flat clouds in these levels are known as altostratus. Unlike cirrus clouds, these formations tend to indicate an incoming storm, and have been known to discharge rain and snow.
The lowest clouds are known as stratus clouds, these are the ones you see the most often. Usually dense, their colouring betrays their intentions, with dark clouds indicating they are waterlogged and could discharge it through rain, hail or snow, whilst white clouds are devoid of any excess water.
Storm clouds have a fairly recognizable name which you may have encountered on more than one occasion: cumulonimbus. These clouds are dark, very large and can reach incredibly high altitudes – at time higher than most airliners, about 15,000 meters (50,000 feet). Storm cloud formations obviously bring forth a large water discharge, thunder and lightning. On top of this, these clouds can be signs of more devastating storm events, such as tornadoes.
These clouds can however be affected by the local environment, notably pollution. Usually, when clouds condense it’s with nothing more than the natural dust in the air, but particles from industry, car exhaust or other such emissions can find their way into the clouds, and eventually into the water that discharges from it. This helps explain phenomenon like dirty rain or acid rain that tend to plague industrial cities.