My DH and I spent a day at the Grand Canyon this week, and while there we experienced a very rare atmospheric phenomenon--a Fire Rainbow or Circumhorizontal Arc.
What is a Fire Rainbow?
It's a rainbow producing light refraction that can only occur during the summer months, and only in mid-latitudes, and only when cirrus clouds are present, and only when the ice crystals in those cirrus clouds are perfectly aligned to produce THIS:
This is a faint one, but it is there for certain in that small patch of cirrus clouds just above the trees. It lasted for about 3 minutes, then was gone.