Cold weather, or excessive heat starts going into nonlethal environmental hardship, over the course of hours. So it could be useful if opponents have no lvl 1 casters for endure elements.
WEATHER .
Wind and rain can interfere with sight, movement, attacks obliterate tracking, force concentration vs arcane casters, blow away small or tiny creatures, or act against ranged projectiles.
A massive amount of precipitation accompanies the harshest storms, resulting in a little over a ton per square per hour.
Unfortunately control weather is not a localized spell, and it only affects the weather in the appropriate locations (IE sky), so it cannot be brought down underground easily. As well, logically most dungeons that have stood more than a year have some method of surviving sudden floods, say porous rocks, drains, high thresholds on doorways, etc. But if you could get it in, at max you can get 1d4ft of snow (or equivalent rain) each hour per square in a 2 mile radius circle.