I didn't even know this was possible.
(Context!: I went for a quick walk just now out of my office (yes, leonardpart6, in Sam Jackson Hall). I got to the 660-foot skybridge between OHSU and the VA Hospital, looked east towards the Willamette River and east Portland -- after a thunder-and-lightning-and-hail-storm, by the way -- and between me and the land below was a rainbow. Cool.)