Red Sky at Morning, Hikers Take Warning…

2010-09-19 18:28:38.000 – Ryan Knapp,  Staff Meteorologist

“Red” sky at night, an observers delight.

In my optics class, we looked at the “truth” in a few of old adages that circulate in American culture. One of them we examined was an old naval adage that went:

Red sky at morning, sailors take warning;
Red sky at night, sailors delight.

But, this adage is far from an “American” adage as it can be traced back to Europe several thousands of years earlier. In 1593, William Shakespeare used a variation of the adage in his poem Venus and Adonis, that went:

Like a red morn that ever yet betokened,
Wreck to the seaman, tempest to the field,
Sorrow to the shepards, woe unto the birds,
Gusts and foul flaws to herdmen and to herds.

In case Shakespeare’s language is a bit much for you, to put it more simply:

Red Sky at morning, y’all take warning.

But even before Shakespeare used the verse, it could be found in an even older literary work, the New Testament of the Bible which reads:

…when evening comes, you say ‘It will be fair weather, for the sky is red,’ and in the morning, ‘Today it will be stormy, for the sky is red and lowering.’…” (Matthew 16: 2-3)

It was different wording but the same adage. Although, it is impressive to think that this adage dated back several thousands of years in some of the oldest literature on the planet, it should be noted that the wording of these verses vary from time to time depending on what version you read. And several earlier manuscripts don’t include these two verses and instead just end with “He replied.” In any case, between the Bibles version, Shakespeare’s version, and the oral traditions in the US and Europe, this adage has been around for awhile.

And, if you live in the mid-latitudes, there is a bit of truth to the adage. Sunrises/sets tend to see the most colorful displays because the sun is at a low angle and passes through more of the atmosphere. At these low angles, the light gets scattered by vapour, water droplets, dust, pollutants, sea salts, etc and certain colors get muted or absorbed while others pass through to light up the sky. The shorter wavelengths (blues and purples) in the light spectrum get scattered out first while longer wavelengths (reds and oranges) pass through. So when there are more particles present during a sunrise or sunset, more of the red is seen as the lower wavelengths get scattered and absorbed.

Storms in the mid-latitudes typically move in a west to east fashion. If you’re on land or sea, if you see a red sky in the morning, it means that light from the sun is passing through dust particles, salt particles and other pollutants on the backside of an exiting high with a low from the west spreading in clouds. If it is a deep red, there is a lot of moisture present increasing the odds of an impending storm. On the other hand, if you see the red sky in the evening, it means the particles that are scattering the light are to the west from a high that is building in with the clouds being provided on the backside of an exiting low.

This rule of thumb works in most instances but not always. A low making the sky red in the morning may rain out before it reaches your location or shift north or south of you leaving you high and dry with just a pretty sky to look at. Not all parts of the mid-latitudes see west to east traveling storms. New England for instance gets powerful systems that come up the seaboard in a more south to north fashion. Parts of Asia even see storms that move east to west at times. Areas with heavy air pollution can sometimes provide false skies as well. And rain right around sunrise or sunset can also create a red sky meaning that unsettled weather is at your location, not coming or leaving per say.

So, why am I going on and on about a red sky? Well, Thursday morning, the sky around the summit was on fire. Having just posted my forecast an hour before the sun actually rose, I already had an idea of what was going to happen but just reading this type of sky, I knew that within 24 hours, rain would be here. And sure enough, a passing low brought us over a half inch of rain. So for this instance, a fiery red sky in the morning rang especially true about the impending weather. So, to throw my hat into the ring of the people who have adopted this adage, I offer you the following rule of thumb:

Red sky at morning, hikers take warning;
Red sky at night, hikers delight.

It’s probably not original but at least it is another tool you can take with you when hiking in the back country. And if you see lenticulars clouds (like this one from last night), be prepared for impending weather as well. But I have gone on long enough, so I will save that for another time…


Ryan Knapp,  Staff Meteorologist

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