The simple answer to the question of weather is, that it's whatever the story requires.

The long answer is that water vapor rises from the center of the Low Sea, but it only reliably fills the lower terraces.

This means that the Low Sea and Green Hell are both inundated with water, but the Emerald Hills and upward are not.

For the Emerald Hills, the Arid Steppe, and the Frozen Wastes, the prevailing winds alternate between day and night. Daytime winds blow from the Low Sea outward, while nighttime winds blow from the Frozen Wastes inward.

Summer and winter have the effect of lengthening the day/night cycle, and thus the giving more variation to the temperatures.

Another factor is the North/South winds, the Northern and Southern latitudes can see wet air traveling to the poles, and then back toward the equator, but much colder and following the upper terraces. This can lead to some intense winter storms.

And also some intense summer storms as well.

The only area spared is the equator, which gets monsoons in the spring and fall. Pouring rain, but little in the way of severe weather systems.

The Frozen Wastes are less frozen at the equator, and the Green Hell actually extends into the Emerald Hills.