Then there's the upside-down rainbow, perhaps the happiest of all rainbows since it looks like a big, multi-colored smile in the sky. Also called a circumzenithal arc, these upside-down rainbows are pretty rare. As the interim president of the Mount Washington Observatory Ed Bergeron explained to SeaCoastOnline, these rainbows only crop up when the the sun and a cirrus cloud are low or parallel to one another. "Typically you see them when you're hiking and you're able to see above the cloud of moisture."
Editor's note: This slideshow was originally published in September 2012 and has been updated with new information.