The only stupid question is the question that goes unasked. You would do well to remember that, Sonozaki-san. ~_~
Oh, and just so you know, the fog doesn't HAVE to be cleared. I went through the entire game without even knowing there WAS a fog clear HM when I played the Japanese pearl.
So nyeh.
And yes, there are varying weathers. But they depend on what part of the map you're in, meaning that for any given area, the weather for that area will always be the same.
About the only thing that changes in any area is the sunlight.