There was a fantastic storm brewing at Lake Powell a few weeks ago, and it did bring some rain, but the clouds, lightning and double rainbow were some of the most amazing I have seen. You add that to a beautiful setting and it is an incredible combination. One of those rare once-in-a-lifetime moments!
I highly recommend that you use a good quality circular polarizer filter when shooting rainbows, clouds, and water. It really pops the colors if you have it turned just right. Don’t forget to twist the polarizer to bring in the best view before shooting.