(SOUTHERN COLORADO) — Winter months do more than just provide snowy days and cold nights, the atmosphere and weather can put on quite a show with just the right conditions. 

You may have seen it yourself, optical shows in the atmosphere from day and night. Sundogs, sun pillars, and halos around the sun, each giving a burst of color and light on an icy day. 

But what are these phenomena and how do they form?

In the atmosphere, under the right conditions, water droplets and ice crystals can act as a prism to visible light showcasing the rainbow within. 

Halo over Calhan. Courtesy: Kristy Balsick

With refracted light and reflected light, this can change what we see within each of these optical effects. 


Just as the name suggests, a halo is a ring of light that forms around the sun or moon. As light from the sun or moon refracts off ice crystals in a thin layer of cirrus clouds, it creates a visible halo. Usually seen as a bright, white ring and sometimes it can have color. 


Sundog. Courtesy: National Weather Service

Sundogs can look very similar to halos but don’t quite have the full ring. Sundogs are colored spots of light that develop with refracted light through ice crystals. These are located either 22 degrees light, right, or both from the sun depending on where the ice crystals are. The colors within a sundog usually go from red (closest to the sun) to blue (farthest away from the sun) outside of the sundog. Sundogs are also known as mock suns or parhelia which means “with the sun”


These pillars appear as shafts of light extending vertically above the sun. We can most often see these at sunrise or sundown. Sun pillars develop as a result of ice crystals slowly falling through the air and reflecting the sun’s rays off of them. Sun pillars are mainly seen when the sun is low on the horizon and cirrus clouds are present. We can also get sun pillars in combination with sundogs and or halos.  

Light pillar in between sundog in Fountain. Courtesy: Greg Heavener

Not only can we get cool phenomena in our atmosphere, but also on the ground when we have icy/snowy days. 

Rime ice, and frost can be common in the right weather conditions, yet one is more common than the other. With our recent storm, many may have seen rime ice without knowing what it is.


Rime ice forms when supercooled droplets from fog freeze and attach onto an exposed surface. It is usually formed on objects usually of a small diameter exposed to the air such as tree branches and plants. 

Rime ice is different from frost because of how it is formed. In most instances, rime ice is formed when the object and the air are both below freezing and liquid drops (e.g., fog) must be present.


For frost, only the object itself must be below freezing and the air can be above freezing. Also, frost usually forms on cold nights when water vapor is present. It does not need liquid droplets, like fog, to form. Send us a picture with the FOX21 Storm Team app (Download it on Apple or Google Play).  

Each of these weather and atmospheric phenomena is a cool sight to see and also can make a great photo! If you see something weather-related, you’d like us to explain or show in your neighborhood.