Is it possible for a rainbow to appear in a cloudless sky?

Question

My question is about a rainbow I saw in June. I saw a rainbow, not in an arc, but more like a "splotch" about 60 degrees from the sun (the sun was not behind me). The sun also had a vivid halo around it, as there were a few very thin clouds. The rainbow, on the other hand, was set against a backdrop of a perfectly blue, cloudless sky. It's stayed in the sky for a half-an hour. Any ideas? I always thought you needed to have water dropplets (ie rain), and it hadn't rained at all!!

Answer 1

No.  You need water vapor to diffract the sunlight.  WHat you saw are called "sun dogs", caused by ice crystals at very high altitude.  They are always 60 degrees from the sun, typically on a cold clear day.  It also happens around the moon once in a while for the same reason.

60 degrees is the diffraction angle of water.

Answer 2

Yes it's possible, you don't always need to have rain to make a rainbow like 'thing'.