There's not an actual statement about Od Laguna or some other force controlling the weather. That's just the reasonable conclusion given the conditions of this world and the weather being normal. And I do believe there is plenty of evidence to say so.
I believe Zabazab's argument is already pretty convincing, but if you want more, there are multiple mentions of heavy rain that treat it as a normal occurrence,
rain causing flooding, taking out a bridge,
the Buddheim Jungle in Vollachia, which is compared to the Amazon Rainforest,
a large portion of the world with year-round snowfall,
and even the "desert" of the world isn't actually a desert and gets enough cloud cover and rain to cool it down.
If that is indeed the most common, then that sounds like the best type to use.