It’s not the desert that bothers me. The difference between a desert and a jungle is humidity and soil nutrients, as we can see in the real world by seeing how the Sahara desert is expanding. A magical Sandstorm could easily have accelerated that development.

What bothers me is that only a few kilometers north is a snow-covered tundra with permanently sub-zero temperatures. That should be possible only if there was an extreme difference in elevation. Mt. Kilimanjaro is snow-capped even though it’s on the same latitudes as many great jiungles and rainforests, but it’s almost six kilometers tall.