As to climate again, I take my inference from what the writers say, as well as remarks made in the series. For instance, in the DS9 Technical Manual the Cardassian climate is specifically referred to as being dry and desert-like
; official literature (such as the Terok Nor trilogy) takes this up.
Besides, if you live on an arid planet you do by definition not have high humidity - you'd get that if you were living in a tropical clime. The environment can't very well be both at once! There's that one scene with Garak and Ziyal in a sauna on the holodeck; that's nothing to do with environmental preferences. I go to the sauna to relax now and again but I couldn't stand living somewhere with permanently high humidity.