SIOUX CITY, Iowa (KCAU) – Winter brings a lot of things, from colder temperatures to snowy scenes. But winter also provides the perfect opportunity to catch a glimpse at some stunning phenomena, like sundogs, halos, and sun pillars.

But what exactly causes these stunning sights?

First things first, two basic concepts to understand, refraction and reflection. Refraction happens when a wave passes from one medium to another, in this case, sun rays through ice crystals. As the wave passes through a medium, again, in this case, the sun rays from the atmosphere through an ice crystal, the wave is redirected due to the change in speed or change in the medium, this, simply put, bends the wave (sun ray). To see an everyday example of refraction, take a look at a straw placed in a clear, see-through, glass of water.

And then there’s reflection, which is essentially when a wave is, instead of passed through a medium, is bounced back to the medium it came from. This is the same general concept of looking in a mirror and seeing your reflection.

One of the most common things you might see is something called a halo. You’ve likely seen this many times on cold winter mornings or evenings. Appearing as a bright, white ring around the sun, sometimes a bit more colorful. These rings form as the sun’s rays are refracted and reflected through ice crystals, found within high level cirrus clouds. This refraction/reflection creates a ring of light in a radius of 22° around the sun.

The next thing you may see at times during the winter is a sundog, scientifically called Parhelion, which is Greek for “beside the sun.”

Sundogs, like halos, appear when sunlight passes through a thin layer of ice crystals, again, found most typically in cirrus and cirrostratus clouds. Like halos, sundogs are most common around sunrise/sunset when the sun is closer to the horizon and also caused by light being refracted through ice crystals. However, unlike halos, sundogs appear as rainbow colored spots on either side of the sun at a 22° angle from the sun. The colors seen come from the refraction, which slows down the sun’s rays to different wavelengths, which results in the light being split into different component colors throughout the visible spectrum as the wavelength changes.

The other, much less commonly occurring phenomenon you may see is sun pillars, which are shafts of light extending vertically above the sun. Like with halos and sundogs, sun pillars are more common when the sun is low on the horizon, like at sunrise and sunset, and with the presence of cirrus clouds and ice crystals within them. However, sun pillars aren’t the result of refraction, instead they occur when ice crystals fall through the atmosphere and the sun’s rays are reflected off them.

While it’s possible to see these phenomena at anytime of year, it’s much more common during the winter months due to a more abundant presence of ice crystals during this time. This higher abundance of ice crystals aloft also coincides with the sun being at a lower altitude, also during the winter months and really creates a perfect storm of conditions for the development of sundogs and halos and sun pillars.

If you see any of these stunning optical phenomena and snap some good pictures, be sure to send us your photos via email (weather@kcautv.com), or social media: