Field Guide / Clouds & Weather Signs
Learn to read the sky before you head out. Search by name or sign, or filter by cloud height and what it usually means.
Cloud signs are rough guides, not forecasts, and they work best alongside the real thing. Check the National Weather Service forecast at weather.gov before and during any trip, and take any watch or warning seriously. If thunder is audible, lightning is close enough to be a danger.
14 clouds
High Cloudsmackerel sky
A high sky of tiny white ripples, like fish scales. It is fairly rare and short-lived, and it often signals changing weather.
Usually means: Weather changing
High Cloudshalo cloud
A thin, milky veil that covers much of the sky and often makes a ring, or halo, around the sun or moon. It is a common early sign of rain or snow.
Usually means: Rain or snow likely
High Cloudsmares' tails
Thin, wispy, hair-like clouds high in the sky. Alone they are harmless, but a spreading and thickening sheet of cirrus can be an early sign of a change in the weather.
Usually means: Weather changing
Mid-Level Cloudssheep's back
Patchy rows or rolls of white and gray puffs at mid-level. Often harmless, but on a warm, humid morning they can mean thunderstorms later in the day.
Usually means: Weather changing
Mid-Level CloudsA gray-blue sheet over the whole sky through which the sun shows only as a dim disc. It often comes before steady rain or snow.
Usually means: Rain or snow likely
Low Cloudsfair-weather clouds
Puffy white cotton-ball clouds with flat bases, typical of a fair day. When they grow tall, they can turn into thunderstorms.
Usually means: Fair weather
Low CloudsA thick, dark gray layer that blocks the sun and brings steady rain or snow for hours.
Usually means: Rain or snow likely
Low CloudsLow, lumpy gray and white rolls that often cover much of the sky. It is a common, mostly dry cloud that can bring light drizzle.
Usually means: Dull and damp
Low CloudsA low, flat, gray layer, like a lid on the landscape. It brings a dull, damp day with mist or drizzle, and it is like fog that has not reached the ground.
Usually means: Dull and damp
Towering Cloudsthunderhead
The thunderstorm cloud: a tall tower with a dark base and, often, a flat anvil on top. It can bring lightning, heavy rain, hail, damaging wind, and tornadoes.
Usually means: Storms possible
Special & Ground-Levelground cloud
A cloud at ground level that cuts visibility and can make it easy to lose your way. Fog that forms on a clear, calm night often burns off by mid-morning.
Usually means: Dull and damp
Special & Ground-Levelflying saucer clouds
Smooth, lens-shaped clouds that sit still near mountains. They mark strong winds aloft and rough air, and they often come before a change in the weather.
Usually means: Weather changing
Special & Ground-LevelPouch-like lobes that hang from the underside of a large storm cloud. They show a strong storm nearby but are not a sign of a tornado.
Usually means: Storms possible
Special & Ground-Levelarcus cloud
A low, wedge-shaped cloud along the leading edge of a thunderstorm. It marks the gust front, where strong winds and heavy rain arrive suddenly.
Usually means: Storms possible