Keeping clouds simple :)
Every official cloud name comes from a small set of Latin words. This guide walks through those words, the ten official cloud types built from them, and a few tips for remembering which is which.
The sky in three layers
Part one
Every official cloud name is built from five Latin words: three describe shape, and two act as modifiers that describe something other than shape — one for height, one for rain. Learn these five, and the ten official cloud types basically name themselves.
Three shapes
Cirrus
cirro- = "curl"Thin, wispy clouds that look like feathers or curls of hair, floating around 6,000m up.
Cirrus clouds are made almost entirely of ice crystals rather than water droplets, because it's so cold at that height. Strong high-altitude winds stretch them into their curled, streaky shape — sometimes nicknamed "mares' tails". On their own they usually mean fair weather, though a growing number of them can hint that a change is on the way.
Cumulus
cumulo- = "heap"Puffy clouds that look like cotton wool or candy floss, usually floating between 300m and 2,000m.
Cumulus clouds form when warm air near the ground rises, cools, and condenses into a heap. Small, isolated ones on a sunny day are called "fair weather cumulus" — the classic cartoon cloud shape. Given enough heat and moisture, a cumulus cloud can keep growing upward all day until it becomes something much bigger (see cumulonimbus below).
Stratus
strato- = "layer"Flat, featureless clouds that don't really move, stretching across the whole sky like a blanket on overcast days.
Stratus forms when a whole layer of air cools and condenses evenly, rather than in separate rising bubbles. It sits low in the sky and can look a lot like fog that never quite reaches the ground. It rarely produces more than a light drizzle, but it's the reason a sky can stay uniformly grey for a whole day.
Two modifiers
Nimbus nimbo- = "rain"
Not a shape — nimbus is added to a cloud's name whenever rain or snow is actually falling from it.
Nimbus describes behaviour, not shape. Attach it to stratus and you get nimbostratus, a steady rain-layer. Attach it to cumulus and you get cumulonimbus, a towering thunderstorm. If you see "nimbus" anywhere in a cloud's name, grab an umbrella.
Alto alto- = "high"
Not a shape either — alto- describes height. Confusingly, it actually marks the middle layer of the sky (roughly 2,000–6,000m), not the highest one.
This is a historical quirk, not a mistake. When clouds were first classified, the low clouds (stratus, cumulus) and the true high clouds (cirro-) were named first. The middle band then got called the "elevated" or "high" version of the low clouds — high compared to stratus and cumulus, not compared to cirrus. So the real order from low to high is: stratus/cumulus → altocumulus/stratus → cirrocumulus/stratus, even though "alto" is the Latin word for "high".
Part two
Weather scientists group almost every cloud in the sky into ten "genera". Seven of the ten combine two of the five words above; the other three (cirrus, cumulus, stratus) are just one of those words standing alone. Either way, the name tells you the shape and the height at once.
Part three
Ten names can feel like a lot to hold onto — but the table below shows the pattern that connects almost all of them.
| Puffy cumulo- |
Layer strato- |
The extra one | |
|---|---|---|---|
| High cirro- |
Cirrocumulus | Cirrostratus | Cirrus the plain, unmixed cloud itself |
| Mid alto- |
Altocumulus | Altostratus | Nimbostratus rain swapped in instead of a mix |
| Low no prefix |
Cumulus | Stratus | Stratocumulus the two mixed together |
Cumulonimbus sits outside this table entirely — a low cumulus cloud that grew tall enough to tower through every layer at once. That makes two "rain" clouds in total: nimbostratus (a flat rain layer) and cumulonimbus (a rain-and-thunder tower). There's no high-altitude equivalent, because anything falling from a high, cold cloud is ice that evaporates before it reaches the ground.