Red sky at night, sailors’ delight. Red sky at morning, sailors take warning.

The phrase “Red sky at night, sailors’ delight. Red sky at morning, sailors take warning” is a traditional weather saying that has been passed down through generations. It is often used as a rhyme to help people remember the association between the color of the sky at different times and the likely weather conditions that may follow.

The saying suggests that a red sky at night is a positive sign for sailors, indicating fair weather, while a red sky in the morning is a warning of potential storms or rough weather ahead. I’ve heard this all my life, but is it true? The rhyme is a rule of thumb used for weather forecasting during the past two millennia.

It is based on the reddish glow of the morning or evening sky, caused by trapped particles scattering the blue light from the sun in a stable air mass. The color changes that we see in the sky have to do with the wavelengths in the color spectrum. As the rays of sunlight bounce off the water vapor in the atmosphere they pass through, they split into the colors of the spectrum.

Red skies suggest that the clouds are filled with a lot of dust and moisture. If there is a red sky at sunset, it is due to high levels of pressure and stable air conditions that are coming in from the west. Because the west is generally the direction that storms move in from, stable air in that direction usually indicates good weather. If the sky is red at sunrise it is generally an indication that dust particles from a storm have passed from the west, moving east and a deep red indicates a high water concentration in the clouds that could mean heavy rain.

The concept is over two thousand years old and is cited in the New Testament. The rhyme has become a rule of thumb, used for weather forecasting on the seas, during the past two millennia. In the Bible, (Matthew XVI: 2-3,) Jesus said, “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.” Shakespeare said something similar in his play, Venus and Adonis. 

“Like a red morn that ever yet betokened, Wreck to the seaman, tempest to the field, Sorrow to the shepherds, woe unto the birds, Gusts and foul flaws to herdmen and to herds.” Using the simple image of the sky to predict the weather may seem slightly oversimplified today when we have the use of such modern technology as Doppler^[1] radar and satellites.

Understanding and applying this traditional saying can provide valuable insights into weather patterns, especially for those who spend significant time outdoors or at sea. However, it’s essential to note that while such sayings can be indicative, modern weather forecasting relies on more comprehensive scientific methods and technology for accurate predictions.