red sky at night, sailors' delight; red sky at morning, sailors take warning

The story

A maritime phrase used for at least two millennia, likely as a shortening of Matthew 16:2b–3: "When it is evening, you say, "It will be fair weather; for the sky is red." And in the morning, "It will be stormy today, for the sky is red and threatening." You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times."