Thin, wispy filaments drawn across an otherwise blue sky — ice crystals swept by jet-stream winds into mare’s tails and hooks. The first sign weather is on the move.

A delicate rippled sheet of tiny white puffs — the classic “mackerel sky.” Each cell is made of supercooled water droplets, no bigger than a finger held at arm’s length.

A translucent ice-crystal veil that dims the sun or moon and produces halos — luminous rings of 22°. The sky looks milky. Rain is usually 12–24 hours away.

Grey-and-white patchy rolls arranged in rows or waves. Larger than cirrocumulus cells, they cast shadows on each other. Morning altocumulus can precede afternoon thunderstorms.

A featureless grey or blue-grey sheet covering the whole sky. The sun appears as though seen through frosted glass — no halo is possible. Prolonged rain or snow likely.

The low, grey blanket that hugs hillsides and coastlines — indistinguishable from fog when it touches the ground. Produces drizzle rather than rain. Otago’s southerly specialist.

The most common cloud on Earth. Grey-white lumpy rolls or patches with clear gaps between groups. Rarely produces significant rain, but can thicken into nimbostratus.

Dark, formless, and merciless. A thick rain-producing sheet that obliterates the sun and delivers steady, continuous precipitation — rain, snow, or sleet — often for many hours.

The classic white cauliflower cloud of a fine day. Flat base, dome-shaped top, sharp edges. Formed by rising thermals. Fair-weather cumulus stay modest; those that keep growing become cumulonimbus.

The king of clouds. A towering colossus spanning the full depth of the troposphere, its top sheared into an ice-crystal anvil by the jet stream. Produces lightning, heavy rain, hail, and tornadoes.