Duathfel is a large enough cavern that it naturally creates its own climate. The warm steam vents and evaporation off the central sea cool near the top of the cavern to create clouds. The Dwemer inhabitants further augmented this natural weather with some of their own technology to create micro-climates suitable for their needs.
I’ve been working on adding different climates and weather to Duathfel. Now, since Duathfel is deep underground, there won’t be any weather patterns like rain or snow, or even day and night. However, there will be regional “weather” affecting various parts of the cavern. This allows me to create different atmospheres and moods for particular places.
Examples
For example, the main city is high up on the side of the cavern. This combined with ventilation systems designed by the Dwemer means the air is clear and visibility is good.
Meanwhile, the rest of the cavern is filled with hundreds of fungal spores, drifting slowly through the still air. Despite the spores, visibility is still good.
The air around the volcanic geyser basin is filled with noxious fumes from many geothermal vents. Embers spew from volcanic craters, and ash falls slowly to the ground. Visibility is more limited here.
Deep in the mushroom forest, the air is thick with thousands of spores. The spores here are even more dense than in the rest of the cavern, limiting visibility.
Update Video
I’ve compiled a video showing the main climates as well as several transitions.
Duathfel 