The 10 main cloud types are easiest to learn by looking at shape first and height second. At high levels, cirrus looks like fine strands brushed across the sky. Cirrocumulus breaks into small white ripples or tufts, sometimes lined up in rows. Cirrostratus spreads into a thin veil that can be hard to notice until a halo forms around the Moon. If you can see three distinct textures on the same day, sketch their outlines separately. A single sky can contain several layers, so identifying one patch does not identify everything overhead.

Altocumulus forms rounded patches or bands. Individual patches often have shaded sides, unlike the tiny white grains of many cirrocumulus fields. Altostratus looks more like a continuous gray or bluish sheet. The Sun may show through as a pale disk. Nimbostratus is generally darker and thicker, with widespread, persistent rain or snow reaching the ground. It can span more than one height layer, so use the precipitation and the broad sheet together as clues. From a window, watch whether the scene is one continuous layer or a field of individual lumps.

Stratus is a low, fairly even blanket, like fog lifted above the ground. It can produce drizzle. Stratocumulus is also low, but the layer has visible lumps or rolls, often with gaps. Cumulus usually appears in individual heaps with flatter bases and rounded tops. Small cumulus clouds often appear in fair weather. To compare them, pick a patch of sky away from the Sun and check it again later. An even ceiling, a lumpy layer and individual heaps will look quite different, even when all three appear white or gray.

Cumulonimbus is the thunderstorm cloud. It can start as a growing cumulus tower and extend high enough for its upper part to spread into a flattened anvil. A nearby storm can hide the anvil from view, so its absence from your window is a poor way to rule out thunderstorm risk. Cumulonimbus can bring lightning, heavy rain, hail or strong gusts. Use a weather forecast or radar to check what is approaching. If thunder is audible, take shelter inside a substantial building or enclosed hard-topped vehicle and leave the cloud watching for later.