Red sky at night, weather delight?

November 01, 2024

“Red sky at night, shepherds delight. Red sky in the morning shepherds warning” this concept first appears in the bible, often said during sunrise or sunset to signify the changing skies and help shepherds prepare for next days weather. Although this remains a popular saying in this modern day there is scientific evidence behind these colourful occurrences.

The fact behind the folklore:

The “red sky at night, shepherds delight” tends to be proven true as red sky at night correlates with impending fair weather. Red skies appear when small dust particles are trapped in the atmosphere due to high pressures. Scattering the blue light leaving only the vibrant red light we all know and look forward to seeing.

However, the “red sky in the morning, shepherds warning” appears when the high-pressure weather has moved towards the east, indicating that the fair weather has already passed and a low-pressure system is yet to come, resulting in a high likelihood of wet and windy weather throughout the day.

The age old saying, only rings relatively true in regions where weather systems are travelling west to east, which includes areas such as the UK.

Although the sun’s rays look white, just like a rainbow the rays are made up of a spectrum of different colours, the sun ray is essentially a wave of energy, and as discussed in our previous blog, "raindrops to rainbows:How they paint the sky" each colour has a different wavelength, with red being the longest wavelength and blue and violet having the shortest. However, the sun emits more energy as blue light compared to violet light, and our eyes are more sensitive to blue light in comparison to violet.

During most the day, skies appear blue because small particles and dust in the atmosphere mainly scatter the blue portion of sunlight. This is most prominent when the sun is set high in the sky, further away from the horizon level. At lower levels, sunlight must pass through more air that it does when it’s higher, therefore by the time the light reaches our capability of sight the blue light has already scattered, leaving only orange and red light.

What can affect the skies colour?

The skies can differ all over the world for a variety of reasons, some examples of this include:

Air pollution: The most heavily polluted areas in the world often experience more intense red and orange sunsets, due to the sheer number of manmade pollutants in the air, annoyingly the sunsets are renowned to be more pleasing to the eye, when in actual fact these red skies are a clear indication of air pollution. Los Angeles regularly experience’s these musky orange skies along with it’s famous high levels of smog in the air. Countries closer to the equator, such as India tend to experience warmer skies due to the humidity and increased levels of pollution and dust in the air.

Natural weather events/ disasters:

Extreme weather events can also change the colours of the sky, due to creating changes in the atmosphere that tend to create difficulty and distance the light rays must travel through to reach our line of sight, in events such as volcanic eruptions and wildfires, large amounts of smoke and gas are emitted, creating increased pollution levels in the area, changing the skies colour from a blue to the domination of vibrant orange and reds.

During hurricanes the increase in water vapour in the atmosphere scatters light leading to the reduction of the shorter blue light and an increase in orange and red light. The dust particles swept up by the high winds of a hurricane scatters blue light further causing more yellow and orange light to break through.

Sandstorms naturally also impact the skies colour due to the dust being swept up into the atmosphere creating the classic sandy orange skies.

Monitoring air pressure:

To monitor the skies from your home and measure atmospheric pressure a barometer is the perfect addition to home weather monitoring. Our range of aneroid barometers are both functional and aesthetically pleasing, ideal for any weather watcher’s wall. Monitor the everchanging skies from the comfort of your own home.

ClimeMET Barometer Dial, CM4300

FAQs:

Where does the “red sky at night” saying originate from?
The ancient maritime and also mentioned in the bible, used for agricultural traditions by shepherds and sailors to predict weather patterns.

How reliable is the saying for predicting the weather?
Although not 100% accurate, the saying is a fairly reliable prediction of short-term weather events especially in regions where winds are coming from the west.

Is this saying used worldwide?
It is predominantly used throughout English speaking countries and in regions with similar weather patterns to the UK. However, there are other sayings that exist worldwide.

Does pollution affect the red sky phenomenon?
Yes, pollution enhances the redness in the sky during sunrise and sunset due to the increased number of particles in the atmosphere, these scatter light more effectively.

Why does the sky appear red during sunrise and sunset?
The red colour is due to the scattering of light by the atmosphere, the sun is low on the horizon during sunrise and sunset, therefore the light passes through more atmospheric particles, scattering the shorter blue wavelengths leaving the warmer red and orange longer wavelengths to dominate the sky.