this is from the 3rd naruto shippuden movie,
In naruto they have, Earth Element is weaker than Lightning Element(Sasuke element) which is weaker than Wind Element which( Naruto Element ). But the wind element is weaker than Fire Element(Sasuke Element) but weaker than Water Element.
As of now Naruto only uses the wind, but maybe in the future he can use the water element.
It could be something to do with storms (thunder clouds?) – but thats more of an ability than an element.
According to the Naruto chakra elements, water is weak against earth but lightning is strong against earth. And as we know, water conducts electricity. Considering these facts I guess it could enhance the attack power of the other chakra element nature.