Cats and skunks are nocturnal. However, since you have seen the cat during the day, and skunks have the added factor of being afraid of humans and therefore avoiding high traffic areas, my suggestion would be to put the trap out during the day. It would be extremely unlikely you would catch any wild animal then. If it should happen that you do trap a skunk, raccoon, possum, etc, you could call animal control and they would likely release the animal. Since they are all nocturnal, if it were wandering around during the day it would most likely mean it was diseased, also, and would therefore be better of being put down.