Question: what are fun things to do in the rain?
Answer: Play out in the rain. Fully clothed or in your swimmers, either way it's going to be so much fun.
Make mud angels. Yep, I said it. ... 
Make a mud tidal pool. ... 
Search for soggy animals. ... 
Make a mud pie or stew. ... 
Raindrop races. ... 
Make a dam. ... 
Search for rainbows.