I thought it was themed around the seasons, with a summer area, a winter area, a mostly-aquatic spring area (which was a pun...'spring') and an autumn area.
Well, I would've thought that the right area would be a fall area too if I would only look at the graphics, but actually the middle area is more of a spring/autumn combination and the "autumn area" is actually a summery room. I just can't draw. My apologies.
The winter area is just a very arctic area, the middle area is a normal area and the... "fall" area is a desert. The CA and the weather changes according to the seasons.
Summer: it will be hotter in all of the rooms, but the winter room will become a 'normal' climate where plants will grow. It doesn't snow in the winter area either, so it's less cold. It will be hotter in the middle area, and the flowers/plants will have less chance to carry edibles. In the desert, it should be too hot for all plants/flowers.
Winter: it will be very cold in the arctic area, in the middle area it will also occasionally snow. The temperature should be perfect in the desert room for vegetation that isn't dependant on water. (It never rains in the desert)
Spring/Fall: 'normal' temperatures in all rooms (cold in the arctic, hot in the desert).
The heat is also dependant on the time of day, mid-day it's hotter than during midnight.