By observing clouds, you can often predict the incoming weather. Clouds have many characteristics and are classified by altitude and type.
Bases start above 20,000 feet, on average
Cirrus: Thin, featherlike, crystal clouds.
Cirrocumulus: Thin clouds that appear as small “cotton patches.”
Cirrostratus: Thin white clouds that resemble veils.
Bases start at between 6,500 and 20,000 feet
Altocumulus: Gray or white layer or patches of solid clouds with rounded shapes.
Altostratus: Grayish or bluish layer of clouds that can obscure the Sun.
Bases start below 6,500 feet
Stratus: Thin, gray, sheetlike clouds with low bases; may bring drizzle or snow.
Stratocumulus: Rounded cloud masses that form in a layer.
Nimbostratus: Dark, gray, shapeless cloud layers containing rain, snow, or ice pellets.
CLOUDS WITH VERTICAL DEVELOPMENT
Form at almost any altitude and can reach to more than 39,000 feet
Cumulus: Fair-weather clouds with flat bases and dome-shape tops.
Cumulonimbus: Large, dark, vertical clouds with bulging tops that bring showers, thunder, and lightning.