The three families
Every cloud belongs to one of three shapes. Cumulus are the heaps — cotton-wool piles built by rising warm air. Stratus are the sheets — flat, grey, layered. Cirrus are the wisps — high, thin, made of ice.
Learn to sort any cloud into heap, sheet or wisp and you are already reading the sky better than most people ever will.
The signs of coming rain
'Mare's tails and mackerel scales make tall ships carry low sails' — high, streaky cirrus (mare's tails) and rippled cirrocumulus (mackerel sky) often arrive a day or so ahead of a warm front and its rain. It is one of the most reliable sky signs there is.
The classic sequence is: wisps high up, then a milky veil, then a halo round the sun or moon, then lowering grey, then rain. Watch the sky thicken through that sequence once and you will recognise it forever.
The signs of settled weather
Fair-weather cumulus — the small, flat-bottomed, cauliflower-topped clouds of a summer afternoon — mean the air is stable and the day is holding. Morning fog burning off to blue means the same.
A sky that is clear at dusk with light falling wind is the oldest 'fine tomorrow' signal in the book.
The cloud that ends events
Cumulonimbus is the thunderhead: a towering heap with an anvil top, dark at the base, growing visibly while you watch. If you see one building on a summer afternoon, the question is not whether it will rain but whether the storm will find you.
This is the one cloud whose message you never negotiate with. When the anvil forms, the outdoor plan moves indoors.
Cloud-reading for your event week
In the week before an outdoor event, start watching the actual sky over your venue at the same hour as your ceremony. Clouds are local: a valley, a coast and a hillside put on different shows from the same forecast.
It will not replace the forecast, and it is not magic. It is the oldest form of paying attention — which, in this craft, is the same thing as the beginning of magic.