Personally, I like powerful items (to a degree) and a one shot hurricane item does not bother me, so long as it was dang expensive and difficult to create.
It could easily cause an "Oh Crap!" moment :)
I would have it take effect over a slightly longer period then 30 seconds. To affect miles and miles of clouds, the magic effect would need to take a while.
What if there were no clouds? I could see them appearing, but 30 seconds?
Now, this really is the equivalent to a magic Atomic Bomb and would need to be treated as such with attendant magical protections, security forces, etc.
An enemy mage could easily teleport (if available) into a city, plant and activate it, and then leave. Go to Comment
I can see this used if the PCs are well acquainted going in, otherwise it is shooting fish in a barrel. Most game groups I've been with would not do anything special to prevent the lantern from being put down.
Could be an interesting 1-off scenario where somehow the lantern was taken aboard a ship. Sort of a form of Speed.
They need to keep it from 'detonating'. Sadly there is a storm a'brewing.