Garrett’s Blog: Moon Halos
Occasionally you’ll see a ring around the moon. The halo appears as the moon light is refracted and reflected at an angle of about 22 degrees. The result is a big ring or halo.
So does a ring around the moon indicate snow?
The answer to this folklore is surprisingly, yes. Ot at least… maybe. Moisture in the upper levels often returns faster than the low level moisture. These rings ofter occur in advance of a storm system so seeing a ring around the moon does mean that snow could be on the way in a few days.