The sky is a constant presence in all of our lives, constantly above us and enormous. When we think of the sky, many of us will picture it as pale and blue on a sunny day – which is a very calming sight indeed.
However, we all know that it can take other forms. In fact, we have all heard the phrase “red sky at night, shepherd’s delight”. But what do these other forms mean? Do we know what actually causes the sky to change from blue to other colors?
For example, what makes the sky turn purple? It may be rare for most of us to see a sky that is the color purple, but it isn’t impossible and it’s a bewitching sight. So what does it mean?
That big question is going to be the focus of our article. In the guide below, you’ll find out all the factors that can cause the sky to change its color to purple.
By the next time you’re lucky enough to see a hypnotic purple sky, you’ll enjoy it even more because you’ll have a better idea of what has caused it.
Why Does The Sky Turn Purple?
To begin with, let’s address the main question. Though you may have heard otherwise, there is no definitive answer to why the sky can sometimes be seen to turn purple.
Instead, there are a whole range of reasons that it can do such a thing, and you’ll learn them all by reading on. It can come down to lots of different factors, such as the weather at the time, as well as what time of the day it is.
The sky is most frequently blue, as you will have noticed, but it can shift to other colors at specific times and conditions. For example, a sky can turn red or orange, as well as a yellow tint. Most of these are during the evening periods, though.
What Circumstances Can Change The Color Of The Sky?
As we’ve just mentioned, there are a lot of different circumstances and factors that can cause the sky to change its color from the typical blue we often see.
It doesn’t just have to be one of these at a time, but can instead be multiple, affecting the color of the sky on an even deeper and more interesting level.
Seasonal Times Of The Year
One factor that can cause the sky to change its color is all down to what time of year it is, particularly which of the four seasons is currently going on (see also ‘Why Does Earth Have Seasons?‘). What do we mean by this?
Well, if it is currently the winter then the sun might appear to be a deeper blue when it’s hanging low in the sky than if it was in an earlier season, like summer.
In the summertime, the sun will be a paler blue when it’s low down. You may have heard the phrase “low winter sun” mentioned before, and that marks it out as something unique compared to the rest of the year.
Different Types Of Weather
A key circumstance that will cause the sky to change its color is that of the weather. For example, picture a storm. If you’ve ever been caught out in a storm, you will have noticed how dark everything is.
This is because it brings lots of clouds, and the sky turns a much greyer color.
On the other hand, the sky can become a much lighter shade of blue when there is a good amount of moisture around in the air. By contrast, the blue will darken when there is less moisture in the sky.
You may be surprised at this, because most of us will think of a blue sky as something primarily related with sunshine. Sun is rarely connected to rain, and yet the sky will be a paler blue when there is moisture in the air.
Speaking of moisture, the more moisture there is in the air, the more humid the weather is.
When it eventually does rain, the moisture is actually leaving the atmosphere. For this reason, the sky will then appear darker during heavy rainfall.
This is all because there are fewer water particles in the air to scatter the light around, and so the whole sky appears darker because the light hasn’t been able to spread as well as it normally might – or would when the moisture is still in the sky.
Different Types Of Temperature
Temperature can technically be involved in the changing of the color of the sky, for reasons you might not expect. When the air gets hotter, it is able to hold more water in it.
When it is able to hold more water, it means that the sky has larger droplets of water in it. Part of what determines the color of the sky is down to the way that light is scattered all around, and part of what scatters this light can be water in the air.
With larger droplets of water present, from the increased heat, it helps to scatter the light into a sort of milk colored haze.
On top of that, the sky is higher when the temperature is hot. The sun is what provides light in the first place, and it being higher allows for more scattering of the light.
Sunrise And Sunset
You will have noticed this one if you’ve ever seen the sunrise, or ever been up early enough to the sun rising in the morning. During both of these periods, the sky turns a bright combination of orange and red.
However, there have been instances in some countries where people get to enjoy sunrises that have shades of purple in them, mixed with lilac and pink. On the whole, though, they will tend to be orange and red.
The reason that a sunset is the color red is because the light is having to travel a further distance to reach you, and therefore we see hints of red and orange in the sky.
We’ve already mentioned how the higher the sun is, the hotter it is and the more the light gets to be scattered. However, the sky can also take on different colors depending on the altitude of yourself, too.
To give an example, if you were to climb a really tall mountain, then you would see the sky in a very different light to people who are back down on the ground, or at lower altitudes than you.
The reason for this difference in the color of the sky is that there are less particles around when you’re at higher altitudes, and particles are needed to scatter light.
With fewer particles around, the light scatters differently than when you’re at a lower altitude, and it therefore changes the appearance of the sky.
For this reason, you can also see plenty more stars than when at lower elevations. With less air between the stars and yourself, there is less atmospheric distortion, and you can see more of what is above us.
There is a certain type of cloud that can help cause the sky to change its color to purple, and that is the “stratocumulu cloud”. These form when it isn’t hot, being created when the air is moist and cold instead.
The clouds consist of ice crystals and droplets of water. These then reflect light from the sun, and that reflection helps to make the sky look like it is purple.
This is especially the case during the periods of sunrise and sunset each day. As the sun is setting or rising, it throws its orange and pink rays across the sky and the clouds.
This red glow reflects the ice crystals and droplets of water that are inside the straocumulus clouds, and the reflection makes the sky look as if it is purple in color.
Explanations For A Purple Sky – What Are The Causes?
Now that we’ve looked at all the different kinds of circumstances that can help to cause the sky to change color, we can look at some of the larger and more general explanations for why a sky might have turned purple specifically.
There are a good few of them, and the purple sky you see could be the result of any.
Solar Radiation Increasing
An increased amount of solar radiation reaching our planet could be a potential cause for the formation of a purple sky.
For the past four decades, the quantity of solar radiation that the sun gives off has been gradually increasing year by year, with almost .05 percent every decade.
With a greater amount of solar radiation coming to the Earth, it can be causing the sky to change its color to purple more frequently.
Activity From A Volcano
Another explanation for a purple sky that you might have come across is all down to volcanoes. When a volcano goes off, or there is volcanic activity, it releases particles of ash into the sky.
These can make the sky look like it is purple, especially when the sun is going to set. The light will scatter in a different way in the presence of this ash.
On top of that, the volcanic eruption releases sulfur dioxide which can then react with the bits in the atmosphere in order to form sulfate aerosols (we’ll get to aerosols next).
These scatter the rays of light from the sun even more, and tint the setting sun a purple color instead of just the traditional orange and red that you would expect to see from a setting sun.
It is also worth mentioning another phenomenon that is caused by volcanic eruption, and one that you might notice if you’ve seen a purple or discolored sky after a volcanic eruption.
The small particles of ash that have been spewed out of the volcano can alter the rays of light from the sun in a special way – they can diffract the rays to create a huge type of corona, which is a large circle of light that typically forms around the moon or sun.
The special type of corona that a volcanic eruption can create is called a “Bishop’s Ring”, and is one of the largest ones that you’ll find. It looks like a blue or brown halo that forms around the sun.
When combined with the hypnotic purple sky that has also potentially come from the volcanic eruption, it adds an extra otherworldly look to it all.
Increase In Floating Aerosols
We just mentioned aerosoles earlier, and these can be another cause for the sky changing its color to purple. But what is an aerosol?
Obviously, we have all heard of the aerosols that we spray on ourselves at home to make us smell better and fresher. However, an aerosol is really a group of microscopic particles that are suspended within a gas.
Some examples of commonly occurring aerosols are things like pollen or the spray from the sea, as well as the volcanic ash that we spoke about earlier in the article.
However, this doesn’t answer how the aerosols affect the color of the sky. To put it simply, it’s all about scattering the rays of light from the sun, a theme that has come up again and again so far.
Aerosols that are suspended in the air cause rays of light from the sun to be scattered into separate, different wavelengths of light (which is the measure of the distance between two crests of light).
This means that when there are more aerosols present in the atmosphere, then more of the sunlight rays are going to be scattered around, and this changes the color of the sky and makes it more colorful than the typical blue we see.
In fact, this leads us to the question of why the sky is blue in the first place. Why blue of all colors?
If you’re wondering why the sky is more commonly blue than any other color, the answer is not as complex as you might think, and is all to do with those wavelengths that we just mentioned.
Blue light has shorter and smaller waves to it, and therefore that allows it to be scattered a lot more than other color lights.
With the light of other colors, their waves are bigger and taller, and it affects the way that they’re scattered and stops them from being scattered as much.
Pollution In The Air
Another possible explanation for the sky changing its color to purple is pollution.
When you hear the word “pollution” you may think about waste, like the pollution we have all over the world, and assume that it will be something like toxic chemicals that people have released into the air.
It certainly can be things such as this, but it can also be a case of “light pollution”, which is when there is too much artificial lighting being used.
Light pollution has certainly become a greater problem over the last century, when electric lighting has become more and more popular, and populations and cities have grown bigger.
There is so much artificial light, in fact, that we can see far fewer stars in the night sky than we used to be able to before electricity was invented, or before it was so widely used all over the globe.
This is a big shame, making the night sky far less attractive.
Of course, light pollution might have also affected the way we see the sky, making it appear purple. However, we will get to that later in the article and cover it in greater detail.
A fifth and final explanation for why the sky might have changed its color from the traditional blue to purple is wildfires. These have a similar effect to the volcanic eruptions that we spoke about earlier, where particles are being released from the wildfire.
These particles go into the air (the atmosphere) and help to scatter the light rays from the sun, which makes the sky appear to be a different color than you would normally expect it to be.
On top of that, the smoke released from the wildfire is also a big cause for the changes in color. The smoke also scatters the light from the sun, and this creates the color red.
Red has the longest wavelength of light. Earlier, we mentioned that blue pretty much has the smallest and shortest wavelengths. They’re on the opposite end of the spectrum compared to red, which is at the top.
As a result of it having the highest wavelength, it appears all around the sky a lot more, at least in instances of wildfires.
Since this is red, you may be wondering how it can relate to a purple sky. The particles and smoke of a wildfire have also been known to add purple hints to the sky, too, and that can be one of the explanations for you seeing a purple sky.
In most cases, you will probably know if there has been a wildfire nearby, or a volcanic eruption for that matter. In those instances, there will be no doubt about what has caused the sky to change its color.
However, there are many other causes, as you can see. If you’re lucky enough to see the rare sight that is a purple sky, then it could be any number of the reasons we’ve just listed.
Speculations For A Purple Sky – What Might Be The Causes?
Of course, the explanations that we just covered are all grounded more in fact. However, nobody really knows what is causing a purple sky when it happens, unless it is explicitly obvious like in the cases of wildfires and volcanic eruptions.
Even then, though, you’re more likely to get an orange or red sky.
With that being said, plenty of people have speculated the reasons for the sky to change its color to purple. These combine a mix of guesswork with the scientific, more thorough facts that we’ve just examined and covered.
In the section below, we’ll look at some of these theories and speculations.
The Pollution Theory
We mentioned a little while back that pollution can help to change the color of the sky, whether it’s chemical type pollution or even light pollution.
However, some people speculate that pollution is responsible in a slightly different way to what you might have expected.
As we all know, vehicles are a major contributor to pollution.
The transport industry is the cause for almost a quarter of energy related emissions of greenhouse gasses, the gasses that have caused global warming and are gradually increasing the temperature of our planet’s atmosphere.
These vehicles release small droplets of sulfur dioxide into the atmosphere, droplets that are mixed with water vapor. This all helps to produce smog, which you will probably have heard of, especially if you live in Los Angeles or San Francisco.
Smog is basically like a fog, a big hazy mist, but it has been emphasized and made thicker through the added pollution. It isn’t just vehicles contributing this pollution, there are other sources and industries, though they are a notable part of it.
Some people speculate that the smog and the sulfur dioxide traces get into our eyes, which causes us to then view the sky as much more purple (or pink) than it really is.
It is debatable how much truth there is to this, but some like to think it as a cause to us seeing purple skies.
It is suggested to particularly happen when the weather is hotter, because the levels of pollution are often higher on these days than when the weather is colder.
This is because the extreme, high heat of a heat wave increases the amount of both particulate (particle) and ozone pollution going on. The stagnant nature of the hot air doesn’t help these pollution levels, either, making them even worse.
The Aurora Theory
Another speculation for what causes the sky to occasionally appear the color purple is that it’s actually an aurora. But what is one of those? You might have heard of the aurora borealis, also known as the Northern lights.
It’s a beautiful and enchanting green and yellow glow of light that hangs in the sky in places around the north of the globe.
From locations such as Iceland, Norway, Greenland, and Canada, you can sometimes see these magical lights floating all across the night sky.
Auroras occur due to a complex and scientific reason. It’s all about particles colliding with atoms of gas.
The particles themselves are electrically charged and very energetic, and they travel along the magnetic field lines and up into the top part of the atmosphere.
In this area, they collide with the atoms of gas, and that makes the atoms begin to give off light. This creates the mysterious light of the aurora.
The “magnetic field lines”, if you’re wondering, are the imagined lines that the North Magnetic Pole would travel across.
As we’ve said, auroras tend to be yellow or green colors, but it can be seen in other shades. These include blue and red, but also crucially include purple.
Therefore, this could be what you’re witnessing when you see the color of the sky change into purple. It could simply be an aurora that you’re witnessing.
With that being said, the chances of it being a purple aurora are far less than seeing a typical aurora of green and yellow shading. It would be a rare occurrence.
On top of that, you would have to be living or located in a place that is known to have auroras visible from it.
As we stated, the most popular and well known of these are visible only in places to the north of the globe, and even then it’s only certain locations – and even, in some cases, certain parts of those countries.
If you’re not in one of those countries that are known for seeing auroras, but you are seeing a sky that has turned purple, then it is unlikely that auroras are the cause of this change.
For that reason, this speculation is only fairly useful. It will most certainly be the true cause in some places, but it won’t be the reason for a lot of other people.
The Ice Theory
Of course, some of these Northern areas are close to big masses of ice. There are some who speculate that ice particles come off these masses of ice, flowing up into the atmosphere alongside other more general dust particles.
These various particles then scatter the light rays from the sun in different directions, sometimes causing the sky to appear as if it is purple. This theory is debatable, but it is easy to see that there could be some truth to it.
We have so far frequently mentioned the effect of particles scattering sunlight, so it is not hard to imagine that ice particles could be contributing to those and having the same outcome.
The Rain Theory
Some suggest that the purple appearance of the sky is caused by varying levels of moisture in the atmosphere. When the air is humid, which means that there is a lot of moisture in the atmosphere, the sky has been known to turn a lighter shade of blue.
This is because there are more moisture particles present in the atmosphere, and therefore a lot more scattering can be done.
Since blue is the color that has the shortest waves, it scatters the easiest, and benefits doubly from having lots of moisture particles in the air to scatter it around.
However, blue is not quite purple. With that being said, the same principle could result in the sky changing its color to purple.
With many more particles in the air for light to scatter off, thanks to the increased moisture particles in the atmosphere, there is technically a better chance for the wavelengths of any color to be spread around – and make the sky appear a different shade altogether.
Purple might just be the shade that scatters around.
When it rains, the moisture is being dropped out of the atmosphere. This means that if you look up into the sky when it’s raining, then you will probably have a hard time seeing anything up there.
This is because there is a lesser amount of moisture particles in the air, and therefore fewer particles for light rays to bounce off and scatter around – whatever the color.
This makes the sky a lot darker, because the light cannot spread as easily as it could before.
The Optical Illusion Theory
This is an interesting speculative theory about why we might sometimes see the sky as purple. More than theory, this is actually research put forward by scientists themselves, and for that reason is likely accurate.
They argue that seeing the sky be a shade of purple could be the result of an optical illusion tricking out eyes, in a sense. It’s all to do with the way that our eyes go about processing the colors that they are taking in.
As you may know, we all see colors a little differently to each other as it is, and color blind people see them even more differently than some other people. The eye is a complex thing, which takes in everything it sees in a unique way.
But how does this relate to the sky specifically? Scientists suggest that it’s all to do with light pollution. Light pollution is all to do with an overwhelming presence of artificial lighting.
As the decades have gone by, electricity has become more and more widely used all over the globe. As a result, there are now billions of different artificial lights in use every day.
Ones such as car headlights and streetlights are some of the biggest contributors to light pollution, because they are a constant presence outside.
If you think about it, I’m sure you’ve noticed local streetlights you have that stay on all throughout the night, even when there is nobody around.
These lights are the reason that we cannot see as many stars in the night sky as we used to, because it affects our eyes and what we can see.
On a more technical level, the light pollution from these types of artificial lights makes our eyes adjust and change, altering so that they can pick up more violent and blue colors.
These are exactly the kinds of colors that will make the sky look purple. Therefore, it is possible that when you see a purple sky, it isn’t actually purple.
Instead, it’s the way our eyes are perceiving it, because they’ve been adjusted by the heavy presence of artificial lights all around us.
Purple Sky: Should You Be Worried?
Since it’s such a startling sight, and very different to the typical blue colored sky that we are used to seeing, you might be wondering whether the sky changing its color to purple is a cause for concern.
Is it possible that it could be dangerous?
After all, the red and orange skies that happen when the sun sets or rises are quite intimidating in themselves, and a person who doesn’t know about them in advance might be worried the first time they see an almost blood red sky looming high above them.
So, is a purple sky dangerous? The answer varies.
Though the presence of a purple sky isn’t going to cause physical issues to the planet (though if it’s a result of a volcanic eruption or a wildfire, then you should stay clear of those dangers), some people speculate that purple skies could have a negative effect on our minds.
A prolonged presence of a purple sky could impact people’s mental health, some scientific evidence has suggested. For that reason, a purple sky could be seen as dangerous.
However, it is likely that the effects would only be felt over time, rather than immediately happen as soon as the sky turns purple. If your mental health isn’t in a good place at the moment, it is a good idea to steer clear of purple skies.
Purple Sky: How Common Are They?
The chances of you seeing a purple sky can depend on a variety of different factors. They are not a common occurrence on the whole, which makes the fact of you seeing one quite a special treat.
In all of the article that you’ve read so far, you will have seen that a sky turning its color to purple can be the cause of a lot of different circumstances.
From pollution to time period, or even location and weather, there are lots of different circumstances that could be the cause of a purple sky. They can even be caused by a volcano erupting.
For that reason, they are not too common. With that being said, it is good that there are a lot of factors that can cause them, because that should technically improve your chances of coming across one.
A common cause for a purple sky is the sun setting or rising. Since the sun does these things every single day, and does them in every area of the world, it increases your chances of coming across a purple sky.
Obviously, make sure to never actually look at the sun itself.
Part of their frequency with sunsets and sunrises is that the sky is usually clear during them, and a clear sky is the perfect condition for purple or blue light to get through the atmosphere.
Purple Sky: How Long Do They Last?
You might be wondering how long a purple sky will last, especially if you’re concerned about the mental health effects it can have that we mentioned in the previous section.
However, the answer can vary a lot. This may not be surprising to you, since purple skies are clearly created by lots of different circumstances, and so it is hardly a shock that their durations can vary a lot as well.
The amount of time that a purple sky will be present for can depend on a range of different circumstances, with things like weather and location influencing how long it remains.
The weather can affect the duration of a purple sky through elements such as wind and humidity. To go into more detail about the weather’s effect, the speed of the wind can change whether a purple sky lasts for longer or shorter.
Additionally, humidity can affect how long a purple sky lasts because the purple light is scattered off moisture particles that are in the atmosphere. This is how a purple sky can be created.
When it is humid, there is a lot more moisture in their air, and therefore a lot more particles of moisture for light to be scattered off. When humidity ends and rain begins, the particles leave the clouds, and the sky becomes darker – the purple sky ends.
On top of that, location also affects how long a purple sky lasts. If you’re in a place that is low down, with a low elevation, then a sky that is purple will likely last for a lot less time than one does when you’re at an area with high elevation.
On the whole, however, a purple sky will tend to stay for anywhere between thirty minutes and an hour. They don’t stay for hours at a time, which only contributes to their rarity.
It is uncommon that you will even see a purple sky, but when it does occur, don’t expect it to stick around.
A purple sky is a sight to behold, because it looks magical and is quite rare. They can be caused by a whole range of different reasons, which you now know about.