I doubt it would be boss related.
http://www.graalians.com/forums/show...hlight=weather

Could be to spawn different types of bugs throughout the day.

For example, ants (I know there aren't any on graal), but they move into houses when it gets humid, going to rain, based on the weather.

Snails (Again, no snails) They move into bushes when it rains, and when it stops they leave.

Fireflies at night, probably spiders too, which you can only spot on trees if you have a lantern. It would have to be somewhat dark though.

But yeah, I guess, if it rains, the insects take cover.

Would be nice if they added more, like wind (gravity-like effect at destiny tower)
thunder (get hit by lightning and you drop a few hearts?)

When it rains, higher worm spawn rate?