Professor Paul Thursday-Is A Red Sky At Night A Delight?

Many weather sayings can be traced back thousands of years. Long before there were weather satellites and forecast models, these phrases were all that folks had in the field of weather prognostication. Those who rely heavily on the weather for their livelihoods, such as sailors and farmers, have been the authors of many of the most popular sayings. Some phrases were more reliable than others at foretelling changing weather conditions. One of the more popular weather adages we will dig into is, "red sky at night, sailors delight; red sky at morning, sailors take warning."  

The first known usage of this phrase occurs in the Bible, in the book of Matthew. This phrase uses the color of the sky at sunset or sunrise as a harbinger of what is to follow. In most areas of the world, weather systems tend to propagate from west to east, thanks to the westerly winds found in the main jet streams of the world. This suggests that when the sun sets in the west, you can read signs in the sky that will tell you what you will experience over the next 24 hours or so. Meanwhile, the look of the sunrise in the eastern sky, can tell you what type of pattern is exiting your area. 

Sunrises and sunsets will have a more reddish tint to them when high pressure systems are in the region. High pressure systems produce a slow sinking air flow from aloft down to the ground. This helps to trap dust and other particulates in the lower atmosphere. These particulates scatter more of the shorter wavelengths of light away before they reach us, leaving the red hues as the ones that become predominant. 

Given that insight, when a sunset is more red than usual, high pressure may be moving in from the west, bringing quiet weather for the next day. Meanwhile, a red sunrise can mean high pressure is moving off to the east of you, meaning the pleasant, quiet weather has passed and inclement weather may be on its way.

No weather adage will ever be foolproof, but it is good to know that science does give some support to this one!