Mackerel sky and mare’s tails make tall ships carry low sails
That’s not actually a weather saying I’d heard of before, but apparently both types of cloud can develop before a storm, hence the shops using low sails.
Mackerel Sky relates to altocumulus clouds, getting its name from the likeness of the cloud formation to the scales on a Mackerel.
Source: metoffice.gov.uk
Weather saying and cloud information courtesy of the Met Office
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