Where do you live? Some places like Florida and such, have high humidity already and is pretty perfect! Here in Ohio, the humidity can be high, but in the summer it gets low, so I have a kiddie pool dig into the ground for her to soak (she uses it too!) and I spray her down with the hose every mid afternoon, when it's the hottest.
i live in kansas. so i assume its around the same as what u are dealing with. i do have the top of a bird bath dug in the groung but im not sure if its deep enough. the kiddie pool idea sounds awesome though!