I received a call tonight from a viewer asking the cause of the large ring around the moon this evening. The rings around the moon are called halos and are the result of moonlight being refracted by ice crystals that make up cirrus clouds high in the atmosphere. The same phenomenon can occur around the sun during the day. More than one halo can occasionally be seen, with the most common halo at 22 degrees in radius from the sun (as a reference, 90 degrees is the sky distance from directly overhead to the horizon). Folklore maintains that halos around the moon or sun means rain or snow should be expected in the next few days. This idea stems from the common occurrence of cirrus clouds a few days ahead of an approaching storm system. Tonight's cirrus clouds are associated with a storm system moving slowly away from the area, so in this case, a rain forecast based on Folklore would be wrong.
Zach
