Are there any other uses for "Clear Sky"?

Solution 1:

Clear Sky got two usages as far as i know:

1. Using it changes the weather to sunny. When you have Auriels Bow, its extremely useful when you cant see the sun.
2. There are some poisontraps around the map, mostly in dwemerruins (e.g. in markarth below the laboratory of calcelmo). The shout will remove the poison, making it possible to walk through it without taking damage.

Solution 2:

Clear sky should indeed clear rain/snow/fog/cloud. It might not be useable in certain areas like Winterhold.

Cleaing the rain/snow/etc can help you see things better, and it can help you if you have certain mods involved that debuffs you during these things (eg. Frostfall/Hypothermia).

Furthermore, Clear sky can be used in the final sets of missions in the main quest. It can be used to clear Alduin's soul snaring fog, as well as his meteor shower shout.