Well, not in of itself but yes: it is a means to activate your bodies natural waste removal system.

Humidity makes you sweat, sweating is a natural way for the body to expunge buildup of toxins near the skin. This in turn helps your skin by not having to grow in the midst of toxin build up. Humidity also doesn't dry out your skin like colder or arid climates do but keeps it moist. Result: healthier looking skin...a.k.a "younger".

This is why people in colder climates tend to use a lot of lotions to hydrate their skin every day. While those in hotter climates can also do this, it isn't nearly as necessary (speaking of the general population...there are of course exceptions) and more of just an "extra step", if you will.

Same applies to someone who exercises a lot: note how their skin looks healthy and vibrant? Sweat.