Sometimes it's plot significant: fog to hide what happens, snow or rain to trap the characters indoors, what have you. And sometimes it's useful for setting mood -- tragedy can happen on a dark and dreary day or ironically, on a bright and sunshiny one.
But -- the thing is about weather is that it's always there as long as your characters ever poke their noses outside. Even when it's not a convenient place to have significant weather.
Your readers may find clear and sunny nondescript enough that you can never specify anything more, and keep the story going without their wondering, but other readers have been known to mind.
On the other hand, there's always the possibility of using it to inspire plot developments -- or sticking it in as local color and find it running about, laughing maniacally, and influencing things all over the place. . . .