Thanks much, guys! We got soaked at the bottom of the cliff, climbed out in the rain, and then it immediately stopped, but the rainbow came out.
Paul, I shot this with Pentax K20D with the ultrawide Sigma 10-20mm lens and a polarizer filter. For the exposure I spot-metered the sky just above the horizon. I like this lens but it can be a bit soft (Sigma is coming out with a better version). For sharper pics I take Pentax DA* 16-50mm. I also have a Canon G10 when going to the mountains.