If the swamps and marshes were dry and the deserts were wet, what would the sky be?

Question

Inside we're wet and outside we're dry
But the weather we do not defy

Losing our heads, we don't go berserk
But this is when we do our best work

Some of us activate with a click
Although human power makes us tick

We're instruments not found in a band
We're useless unless given a hand

What are we?