I got this idea from the Internet, I'm sure.
We had rain all last week. And it's coming back in a few days. This rainy day activity took up a total of 10 minutes, but that's 10 minutes that the kids weren't crawling on me, so that's a plus.
I bought some watercolor paper at the store and Margaret and I dripped food coloring on the sheet and then put them out in the downpour. Observe:
We brought them in and let them dry. Margaret's is the one on the right. Mine is on the left. Since we don't use food coloring any more, this was a great way to put it to use.