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Everyday Mysteries: Fun Science Facts from the Library of Congress

Is the old adage “Red sky at night, sailor’s delight. Red sky in morning, sailor’s warning” true, or is it just an old wives’ tale?

Within limits, there is truth in this saying.

Have you ever heard anyone use the proverb above?

Shakespeare did. He 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.”

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.”

Weather lore has been around since people needed to predict the weather and plan their activities. Sailors and farmers relied on it to navigate ships and plant crops.

But can weather lore truly predict the weather or seasons?

Weather lore concerning the appearance of the sky, the conditions of the atmosphere, the type or movement of the clouds, and the direction of the winds may have a scientific basis and likely can predict the weather.

In order to understand why “Red sky at night, sailor’s delight. Red sky in morning, sailor’s warning” can predict the weather, we must understand more about weather and the colors in the sky.

Usually, weather moves from west to east, blown by the westerly trade winds. This means storm systems generally move in from the West.

The colors we see in the sky are due to the rays of sunlight being split into colors of the spectrum as they pass through the atmosphere and ricochet off the water vapor and particles in the atmosphere. The amounts of water vapor and dust particles in the atmosphere are good indicators of weather conditions. They also determine which colors we will see in the sky.

During sunrise and sunset the sun is low in the sky, and it transmits light through the thickest part of the atmosphere. A red sky suggests an atmosphere loaded with dust and moisture particles. We see the red, because red wavelengths (the longest in the color spectrum) are breaking through the atmosphere. The shorter wavelengths, such as blue, are scattered and broken up.

Red sky at night, sailors delight.
When we see a red sky at night, this means that the setting sun is sending its light through a high concentration of dust particles. This usually indicates high pressure and stable air coming in from the west. Basically good weather will follow.

Red sky in morning, sailor’s warning.
A red sunrise reflects the dust particles of a system that has just passed from the west. This indicates that a storm system may be moving to the east. If the morning sky is a deep fiery red, it means a high water content in the atmosphere. So, rain is on its way.

To learn more about weather lore and proverbs see the following Related Web Sites and For Further Reading sections.

Related Web Sites

Sky Watch; Signs of the Weather, by Jerry Wilson - This article contains information on weather lore focusing on clouds, moisture, and air pressure. Also included are general weather lore and a glossary of weather terms.
Stalking the Wild: The Magazine of Outdoor Discovery - How to forecast weather by nature. Discussions on how certain weather proverbs have a scientific basis. Different proverbs are highlighted along with an audio clip from Tommie Bass describing how weather was predicted in 1900.
Weather Forecasting Through the Ages, by Steve Graham, Claire Parkinson, and Mous Chahine - This article from the Earth Observatory at NASA discusses the history of predicting weather.
Weather Proverbs. True or False? - This Web site discusses weather proverbs that, under the right circumstances, hold up to science.