There is an old sailor’s adage that goes like this, red sky at morn, sailors take warn, red sky at night, sailor’s delight. The origin of the saying is unknown, but a form of it appears in the bible (Matthew 16:2-3). Jesus said: “When in the evening, ye say, it will be fair weather: For the sky is red. And in the morning, it will be foul weather today; for the sky is red and lowering.” Shakespeare also referred to this proverb in his play, Venus and Adonis. “Like a red morn that ever yet betokened, Wreak to the seaman, tempest to the field, Sorrow to the shepherds, woe to the birds, Gusts and foul flaws to herdsmen and to herds.
The saying has some basis in science. In the mid-latitudes of the Northern Hemisphere storms generally track from west to east, following the path of the jet streams. A red sky at dawn indicates that the sun is rising in clear skies and is shining on approaching storm clouds to the west. The red dawn is caused by the sunlight reflecting off of these approaching storm clouds. At night the clear sight of the red setting sun would tell sailors that no storms are to the west. The colors in the sky are due the spectrum of the sun’s light being split as it passes through the atmosphere. Red is the longest wavelength that we can see. Its long wavelength allows it to pass through more dust and water vapor then any other color that we can see. So when the sun is low in the sky it is the color red that comes through when none of the others can.