A sun halo, also known as a sun ring, popped up in the sky this afternoon. The high clouds moving in from Hurricane Ian are providing the ice crystals needed to make the ring. These are fun to catch and can, at times, help tell you what is in the weather forecast.
In weather folklore, you may hear, or read, that “a ring around the sun or moon means it will rain soon.”
Read on to see why this is both true, and not true.
How a sun halo or sun ring is created
A sun halo is a circle around the sun. It happens when the sun’s angle to high-level clouds directs sunlight to the ice crystals of the clouds. High clouds are made of tiny ice crystals.
The light is refracted from the ice crystals and creates a prism causing the rainbow color from each.
The angle of the sun and the person seeing the halo has to be at a certain threshold.
This dispersion of light with the ice crystals creates the ring around the sun called a sun halo.
This also happens at night with the moon. It is called a moon halo.
Does a sun halo forecast the weather?
The answer to the question if a sun halo can predict the weather is both yes, and no.
The halo is produced from ice crystals of high cirrus clouds. High cirrus clouds can be a sign that a warm front is moving toward a region. These high cirrus clouds will slowly build way up high in the atmosphere as warmer air is forced upward over the top of colder air.
The cirrus clouds are typically the first type of clouds to form as a warm front moves toward an area.
Why the sun halo can forecast the weather
The sun halo is formed from ice crystals in cirrus clouds. The cirrus clouds could be a sign that a warm from is approaching the area. If that is the case, you could expect warmer temperatures to move in as well as thicker clouds as the warm front approaches. As the clouds get thicker, you may experience precipitation.
So, yes the sun halo, or moon halo, can be a good indicator that a warm front is approaching and that precipitation may follow soon.
Why the sun halo does not forecast the weather
The ice crystals in the sky may not always be from the process of a warm front developing. They could be leftover from big towering thunderstorms a long distance from your location. They may also be there as a warm front approaches, but it slides south of your region and the weather does not change as the front does not move through.
In the end, the sun halo is a great thing to catch and makes for fantastic pictures, but it is not a great weather forecaster all of the time. It may be hard to tell what is causing the high-level ice crystals resulting in a forecast that does not have a solid base.