Long before weather apps, people read the sky. It is still worth learning, and the basics fit on a postcard.

High, thin wisps called cirrus are made of ice crystals. On their own they mean fair weather, but when they thicken into a milky veil over a day, they are often the first sign of an approaching front and rain.

Puffy cumulus clouds with flat bases are typical of a fine afternoon, formed as warm air rises from sunlit ground. When they grow tall and dark, towering into cumulonimbus with flattened, anvil-shaped tops, expect heavy showers or thunder.

A low, even grey layer of stratus brings drizzle and dull days. Fog is simply stratus at ground level.

None of this replaces a forecast, but it makes every walk a little more interesting, and now and then it will tell you to take the umbrella when the app said not to.