May 03, 2023
How to Know When an Amazing Sunset Will Happen
Why are some sunsets so fiery and spectacular, that they make us stop in our tracks, whip out our phone, and take a photo?
And why are some sunsets just kinda... average?
What makes the difference between the two?
Clouds Provide the Magic
If we watch a sunset on a clear evening, it can be a beautiful view:
But this isn't the sky-on-fire type of sunset that I'm taking about.
It might feel counter-intuitive, but the best sunsets happen on partly cloudy days. These fiery sunsets are caused by the Sun's light hitting the bottom of these clouds. Here's a few examples:
Just a few clouds
This can make for some nice cotton candy-looking clouds. Very aesthetic!
A few more clouds
Here, the sky is a reddish-orange buffet.
Let's go nuts
These are the show-stoppers.
The Sun Needs a Clear Path
Of course, too much clouds just make for a cloudy sky. Not cool.
What we need is for the Sun to be setting on the horizon and have a clear path for its light to hit the bottom of the clouds above us. In fact, you could have a canopy of clouds above you covering most of the sky, but if there's just enough clearance on the horizon for the Sun to peak its head through and shine on the bottom of the clouds, you should be in for a good show.
Why do some clouds at sunset appear yellow and orange, and others appear red and pink?
In short: when sunlight has to go through more air to reach the clouds, the more red it will appear.
In my rough, not-to-scale diagram below, you can see the Sun setting below the horizon. Light is leaving the Sun, traveling through space, and going through Earth's atmosphere.
Notice that the clouds closer to the horizon appear yellow. The light that hits them has to go through the least amount of atmosphere. The orange clouds are a bit further from the horizon and the light has to go through even more atmosphere. Finally, the red clouds are even further from the horizon, and light goes through a lot of atmosphere.
Light is made up of all the colours of the rainbow. Remember ROYGBIV?
Well, when light goes through just a bit of atmosphere, the red, orange, and yellow light wavelengths are all able to reach the first cloud. It appears yellow.
When light goes through more atmosphere, those yellow wavelengths of light get scattered. We're left with just the orange and red wavelengths of light. The cloud appears orange.
And when light goes through a lot of atmosophere, the orange wavelengths are scattered. So we're left with only the red wavelengths of light reaching the cloud and making it look a pretty pinkish-red.
Spotting Pinkish-Red Clouds
These clouds are really gorgeous to me, and I keep my eyes open for them. One way is to the look in the opposite direction of the sunset to the East.
Remember: the light has to go through more atmosphere to reach these clouds. Here's some pink clouds after a rain storm from 2020:
Another way that light goes through more atmosphere is for high-altitude clouds. These would typically appear in the West, in the direction of the Sunset.
High-altitude clouds are usually icy cirrus clouds, and can make an incredible effect:
How to Predict Fiery Sunsets
Now you know that sky-on-fire sunsets need:
- some clouds
- a path for the Sun to reach those clouds in the western sky at sunset
This combo happens on partly cloudy days. My recommendation is to keep an eye on your weather apps for partly cloudy skies around sunset time.
That's the recipe for these majestic views.