Oo. Love the map of how the planes interconnect. Basing your climate on that seems to be the way to go to me.

I'd place several celestial bodies in the sky. At any point on your material plane a celestial body will appear to travel the same course. However, as you move, the celestial bodies will appear to track different courses across the sky. Over the course of a year the different bodies will brighten and pale, causing seasonal changes.

Does that work for you?