You can find a rainbow even on sunny, dry days with this fun project. My kids love treasure hunts, and this one is a classic. Take an empty egg carton and paint the cups with rainbow colors (or for more of a challenge all greys or greens...) and head out.
We try to have both natural examples as well as some alley trash. This is fun but also good for encouraging close looking. And as usual, as we walk, our minds loosen up and we start coming up with new ideas, projects and dreams. A good time spent for all. Happy hunting!