Oddity

Having long ago lost the ability to comment intelligibly, never mind intelligently, on anything at all, I present this picture I took on the way home a couple of weeks ago. There was this weird rainbowish thing in the sky, only not exactly a rainbow, because 1) it went almost straight up and down — well, rainbows do that sometimes, but this seems to be an arc of a circle around the sun, not opposite the sun 2) it wasn't raining. So what is this thing? Anyone know? (My apologies for the through-the-windshield picture. It's the best one I got. Click to embiggen, not that that will help much.)