There exists an old wives’ tale you may have heard of that goes something like this: “Red sky at night, a sailors delight. Red sky in the morning, sailors take warning.”

Image courtesy: loc.gov

Weather tales like this have been around for centuries allowing sailors, farmers and others to predict weather around their daily work and activities, but is there any truth to this old saying? Can the color of the sky really tell us what the weather will be like? Believe it or not, there is actually an element of science to this old tale based on the color we see in the sky and the current atmospheric conditions. Let’s break it down:

The colors we see in the sky are dependent on how sunlight passes through the atmosphere, is scattered off of water vapor and other particles, and then ultimately reflected back to our eyes. Depending on the amount of particles in the atmosphere, the sun’s light are scattered differently.

Photo courtesy: web.pa.msu.edu

Visible light from the sun is made up of colors of the rainbow that contain different wavelengths of light as they pass through different objects. The red colors on the spectrum contain longer wavelengths than the blues and purples as shown in the image above.

NOTE: At both sunrise and sunset the sun is at its lowest point in the sky and shining through the thickest and most dense part of the atmosphere.

What it comes down to is that dust particles and water vapor present in the sky are able to scatter longer wavelengths of light more efficiently, so the reds are what you see in the sky as a result. A cleaner sky containing less dust particles is able to scatter shorter wavelengths of light more efficiently, and therefore why the sky appears to be blue!

Image courtesy: esrl.noaa.gov

Individually broken down like so:

RED SKY AT NIGHT, SAILOR’S DELIGHT

-Weather generally travels from west to east, so if you can see a nice sunset, that assumes there are clear skies west (sun sets in the west), heading toward you. Calm weather to be expected.

RED SKY IN THE MORNING, SAILOR TAKE WARNING

-The sun rises in the east, so that assumes the clear skies are already to the east, since weather generally travels from west to east in the northern hemisphere.

~Meteorologist Christine Gregory