Clouds 101

Cumulus: In Latin, this means "heap." Cumulus clouds look like a heap of cotton balls or whipped cream.  Cumulus clouds are low individual billowy globs that are low, have flat bases and look a little like cauliflower. They are at least as tall as they are wide and form on sunny days from pockets of rising air. Their constantly changing outlines are fun to watch because they can take the shapes of almost anything, including animals and faces. Cumulus clouds usually signal fair weather. If they build into the middle or high part of the atmosphere they get the name cumulonimbus. A cumulonimbus cloud is tall, deep and dark and can bring lightning, heavy rain and even severe weather such as hail, damaging winds or tornadoes. It is a sign of rapidly rising and sinking air currents.

Stratus: It's Latin for "covering" or "blanket." Stratus clouds look like a flat blanket in the sky.  Stratus clouds are layered and cover most of the sky. They are much wider than they are tall. If you see them in broken or puffy layers, they are stratocumulus clouds. If you see them in thin high layers that turn the sky solid white, they're cirrostratus clouds. The tiny prisms of ice in a cirrostratus layer can bend the sun's light. As a result, often you can see a halo or veil of rainbow colors around the sun. When stratus clouds are very thick, they become dark nimbostratus clouds, which can produce rain, drizzle or snow.

Cirrus: It's Latin for "curl." Cirrus clouds look like curls of white hair.  Cirrus clouds are high and thin and made entirely of ice crystals. Forming above 20,000 feet in the atmosphere, they often look like wisps of white hair. Cirrus clouds, which are a sign of warm moist air rising up over cold air, are sometimes an early signal that thickening clouds could bring light rain or snow within one or two days

Too Clean for Clouds? Our air has to be just a little bit dirty for clouds to form. That’s because water vapor needs a surface on which to condense. Fortunately, even the cleanest air has some microscopic particles of dust, smoke or salt for water droplets to cling to, so the air is rarely too clean for clouds to form.