A sundog is a set of two short rainbows, one on each side of the sun. I used to think that they were caused by extreme cold because they only appeared on the coldest days in Minnesota, but apparently that is not the case. According to one site I found, "Sundogs reveal that the clouds are hosting horizontal plate crystals. These plates drift slowly downwards like leaves with their large faces almost horizontal. [They] are formed when light passes through crystal side faces inclined at 60° to each other."
Sunday, February 22, 2004
A short science lesson for those of you who are less informed: