I'm not sure what to wear tomorrow?

So tomorrow, my friends and I are planning on going to the zoo. It's supposed to be rainy and hot (75 degrees high). I thought I would wear a light, cotton top and some bermuda shorts, but I'm not sure what shoes to wear. I don't want something too open (like flip-flops or sandals) because the ground is going to be muddy from all the rain. At the same time, all my rainproof shoes will be way too hot for my feet. Any advice?