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.