Why is red sky in morning a warning?

Red sky at night, sailors' delight. Red sky at morning, sailors take warning. The rhyme is a rule of thumb used for weather forecasting during the past two millennia. It is based on the reddish glow of the morning or evening sky, caused by haze or clouds related to storms in the region.

By: Brittney Merlot

Posted at 8:18 AM, Aug 05, 2021

and last updated 2021-08-05 09:25:17-04

RED SKY IN THE MORNING, SAILORS TAKE WARNING & RED SKY AT NIGHT, SAILORS DELIGHT: Is this folklore true? The concept is over two thousand years old and is cited in the New Testament. The rhyme has become a rule of thumb, used for weather forecasting on the seas, during the past two millennia. It is based on the reddish glow of the morning or evening sky, for mariners to prepare for what's to come that day... and Meteorologist Brittney Merlot says the concept is mostly true! Here's why...

During sunrise and sunset the sun is low in the sky, and it transmits light through the thickest part of the atmosphere. Red is the longest wavelength in the spectrum and can reach an atmosphere loaded with dust and moisture particles. Once it hits that, red light is reflected back to us and we see a red sky.

When we see a red sky in the evening, this means that the setting sun in the west is sending its light through a high concentration of dust particles to the east. This indicates a low pressure storm system is departing the area, while a high pressure system is arriving and stable air coming in from the west: meaning good weather will follow.

A red sunrise, indicates that a low pressure storm system is moving in from the west. This is as the sun rises in the east and hits high water content off to the west. A morning sky that is a deep, fiery red can indicate that there is heavy rain and high winds on its way.

In the video above 👆 Meteorologist Brittney Merlot breaks it down for you and explains how the prevailing winds are the main reason why this is true.

Sometimes the sky appears very colourful around sunrise and sunset. At these times, the sun shines from a low angle. Sun rays have to go through a thick atmosphere, resulting in scattering by water vapour, water droplets, dust particles etc. in the air. Light with shorter wavelength, e.g. cyan, blue or purple, is scattered away, leaving red, orange and yellow, turning the sky reddish.

In mid-latitude region, storms and rains usually move from west to east. A reddish sky around sunrise means a lot of water vapour already present in the atmosphere. As clouds come in from the west, rainy weather is thus expected. This explains why "Red sky in the morning, sailors take warning".

A reddish sky near dusk means that weather has improved in the upstream area to the west. Sunlight scattered by the atmosphere is reflected by clouds, making the sky red. As the clouds overhead have moved eastward, the weather is expected to improve. That explains why "Red sky at night, sailors delight".

The relationship between red sky and weather is rather complicated in real life. One example is that near dusk, the sky can become reddish temporarily after rain. Besides, especially in low latitude areas such as Hong Kong, weather systems sometimes move from east to west, e.g. typhoons, and not from west to east. Therefore, one cannot fully understand how the weather changes simply by just looking at the colour of the sky. To make an accurate weather forecast, it is necessary to take account of other weather factors and carry out a full analysis.

Why is the sky red at 6am?

An orange or red Sun in the early morning or late evening is a sight to behold. The sky takes on these vivid hues due to a phenomenon called Rayleigh scattering.

What does red sky at night Shepherd's Delight Red Sky in the Morning Shepherds Warning mean?

proverb A red sky at sunset is a sign that good weather will follow. The full phrase is "Red sky at night, shepherd's delight; red sky in the morning, shepherd's warning." I think we're going to have a nice sunny day tomorrow. Look at that sunset—red sky at night, shepherd's delight.