By Bill Willis and Bill Steinmetz
March 7, 2018
What is the truth behind this old saying, “Red sky at night, sailor’s delight. Red sky in morning, sailor’s warning.”? Could the sky foretell past or upcoming weather events? What does looking toward the east in the morning indicate or is it a warning that we best look to the west in the evening?
Turns out that this old saying has restrictions placed on it. It is most meaningful between Northern latitudes 30o to 60o mid-latitude and over water. In this latitude, storms and accompanying winds move from west to east.
The following excerpt is taken directly from Fun Science Facts from the Library of Congress and describes this phenomenon.
“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 reflect off of 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 can mean that a high-pressure system (good weather) has already passed, thus indicating that a storm system (low pressure) may be moving to the east. A morning sky that is a deep, fiery red can indicate that there is high water content in the atmosphere. So, rain could be on its way.”
This saying is often true over land, however, there are exceptions. Fires, dust storms or pollution can intensify the red colors providing false interpretations.
Pictures were taken from the NIEHS facing eastward toward EPA before 0700 hours. The pictures provide a range of colors and atmospheric conditions.