Weather Explainers

Red Sky At Night: Real Science Behind The Age-Old Weather Saying

"Red sky at night, sailor’s delight. Red sky in morning, sailor’s warning” is real science. Here’s how dust, atmospheric pressure and light scattering can help you predict the weather.

For centuries, the saying "Red sky at night, sailor’s delight. Red sky in the morning, sailors take warning" has been used to predict the weather – but is there any truth to it?

According to meteorologists, this old adage is more than just folklore; it’s rooted in real science. First, two quick atmospheric science lessons:

Westerly Winds

Most of the United States sits in what is referred to as the "mid-latitudes," meaning most states fall between 23 degrees to 66 degrees from the equator. In the mid-latitudes, weather generally moves from the west to the east due to dominating westerly wind patterns.

This means that the conditions in the western sky during sunset can provide a glimpse into the weather ahead, whereas skies in the east may signal what has already passed.

(MORE: Explaining 'Baffling Wind' Nautical Terminology)

Red Skies

The colors we see in the sky are the result of sunlight interacting with particles in the atmosphere. Shorter wavelengths, like blue, scatter more easily, while longer wavelengths, like red, can penetrate through dust and moisture.

That means when the sky turns red, it indicates that the sun is shining through an atmosphere filled with dust and other particles. These conditions are often associated with high pressure and fair weather.

Putting It All Together

A red sky at sunset (night) means high pressure is likely moving in from the west. This suggests clear skies are on the way, hence the phrase “sailor’s delight.”

Conversely, a fiery red sunrise means that high pressure has already passed, leaving behind moisture-rich air and signaling that a storm system could now be approaching – hence, “sailors take warning.”

(MORE: Does A Full Moon Control The Weather?)

While this saying holds true in regions with westerly winds, it doesn’t apply everywhere. Near the equator, where trade winds dominate, weather patterns move differently, and the opposite saying might be true.

So the next time you see a blazing red sky, take a moment to appreciate the atmospheric science behind it. Whether it’s a “delight” or a “warning,” nature could be giving you a heads up on tomorrow’s forecast.

That all said, these sayings should be used as guidance rather than rules of thumb. They won't always be correct. For instance, wildfires in the area can produce smoke that can turn skies red at any time of the day.

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