Red sky at night, sailor's delight...

red sky at morning, sailor’s take warning.

What, if any, science is behind this admonition?

If there’s a red sky at sunset, it means there aren’t any clouds over the horizon to the west. No clouds, no rain overnight, and you’ll have clear skies for sextant readings. Don’t know about the morning part.

It works for the common pattern of winds in the Westerlies. The red sky is indicative of a high pressure system in that direction. A red sky at night means a high pressure system to your west coming your way, and in the morning a high pressure system moving away from you - a low associated with a storm is probably moving in. Here’s an explanation from NOAA:

If the winds are predominantly east to west, you’ll have to dream up a reverse adage.

Here was our last go-round with this question. (I agree with some posters, there, that Cecil has addressed it, bu I can’t find it in the archives, either.)


Yabob’s NOAA link was very informative, but I don’t believe that’s the answer. I’ve always believed, and continue to believe, that the answer is as follows. In the morning, a red sky means the sun is being refracted by a thin layer of clouds coming in from the west. A storm is coming, but the clouds have not thickened to the point that they block the rays completely. In the evening, a red sky means that the sun is being refracted by a thin layer of clouds moving out to the east. The storm is going, but there remain some clouds to refract the light.

I’ve always believed the “red” refers to the red clouds, clouds refracting the sunlight, not to some atmospheric pollutants.

The whole quote is:

“Red Sky at Morning, Sailors take Warning;
Red Sky at Night, Sailors Delight”

(I guess it doesn’t take much to make sailors happy!)
When the wind is in the North
The skillful fisherman goes not forth;

When the wind is in the East
'Tis good for neither man nor beast;

When the wind is in the South
It blows the flies in the fish’s mouth;

When the wind is in the West
There it is the very best.

(Riviere, Bill “The L.L. Bean Guide to the Outdoors”)
ISBN 0-394-51928-0