Rainbow?

This unusual optical effect in the sky was visible when I left work, and still visible by the time I got home.  

We have had NO rain today, and there doesn't seem to be any prospect of any.  In fact, I think it's been a very pleasant autumn day.  Also, the rainbow was much brighter than usual, with this "flare" visible.  When I first spotted it, the flare was so bright, I thought briefly it was the sun, until I looked more closely, and noticed the rainbow spreading up and down from it.