Q: Is the saying "red sky at night, sailor’s delight, red sky at morning, sailor take warning" really accurate?
A: Generally, the answer is yes, says Brent McRoberts of Texas A&M University. The saying has been around for thousands of years and is even mentioned in the Bible in the book of Matthew: "When in evening, ye say, it will be fair weather, for the sky is red; and in the morning, it will be foul weather today, for the sky is red and lowering." The saying, McRoberts notes, "may be the most famous of all weather lore. It goes back to the observations made by sailors who had a clear 360-degree view of the horizon from the ship’s masts. In the northern hemisphere, most weather patterns move from the west to the east, so if a sailor could see a red sunset to the west, it meant that skies were clear in that direction and that tomorrow would likely be a nice day with few clouds."
Q: What is the science behind the saying?
A: When the sky is red at night or sunset, it is caused by the sun striking particles in the atmosphere. "But if a sunrise has a reddish tint or looks rosy colored, and you can see clouds over the horizon, it might mean the nice weather has passed and a storm system is headed your way," McRoberts adds. "It means an area of low pressure could be moving in, and low pressure almost always means clouds and often rain or thunderstorms."
Weather Whys is a service of the Depart. of Atmospheric Sciences at Texas A&M University.