Read the sky by learning how clouds form, change, and signal weather.
Explore cloud types, including high, middle, low, vertical, rain-bearing, and unusual clouds.
Cirrus, cirrostratus, and cirrocumulus form mostly from ice crystals high in the troposphere.
Learn MoreAltostratus and altocumulus occupy middle levels.
Learn MoreStratus and stratocumulus develop near the ground.
Learn MoreCumulus clouds grow upward when warm air rises and cools.
Learn MoreNimbostratus brings widespread, long-lasting rain or snow.
Learn MoreLenticular clouds form smooth lenses near mountains, mammatus hang in pouches beneath storm anvils, and noctilucent clouds glow after sunset at extremely high altitudes.
Learn MoreCirrus, cirrostratus, and cirrocumulus form mostly from ice crystals high in the troposphere. Thin cirrus can arrive ahead of a warm front, while a broad cirrostratus veil may create halos around the Sun or Moon.
Altostratus and altocumulus occupy middle levels. Altostratus often spreads into a gray sheet before steady precipitation, while altocumulus appears as rounded patches that can reveal moisture and instability aloft.
Stratus and stratocumulus develop near the ground. Stratus makes a flat gray layer similar to lifted fog; stratocumulus forms rolls or clumps and usually produces only light drizzle.
Cumulus clouds grow upward when warm air rises and cools. Small fair-weather cumulus may stay harmless, but strong rising air can build towering cumulus and eventually thunderstorms.
Nimbostratus brings widespread, long-lasting rain or snow. Cumulonimbus produces heavy showers, lightning, hail, gusty winds, and sometimes tornadoes as powerful updrafts and downdrafts interact.
Lenticular clouds form smooth lenses near mountains, mammatus hang in pouches beneath storm anvils, and noctilucent clouds glow after sunset at extremely high altitudes.