This would only be necessary if the werewolf had trouble controlling the transformation, or if they had perfect control, but thought that a sudden need might arise. In either case, I would expect a werewolf to purchase a bunch of super-waterproof plastic clothing bags (like the "space bags" I see advertised on TV all the time) and put a change of clothing in each one, and then bury 6 or 7 clothing stashes where they might be needed, say, every half mile or so in a wide circle centering on home.WWs would (I think) have stashes of clothing/shoes hiden around their territory/town they live in. Maybe hidden in dens or waterproof bags or something.
For example, imagine that the werewolf came home but then saw an unexpected guest was already there (perhaps even a werewolf hunter!). The werewolf would want a stash of dry, clean clothing a little distance from the house, in a hidden gully or something where they could change unobserved. Then they could come back to the house.
You wouldn't want to do that all the time, though. Digging up clothing stashes would get tedious and expensive (say, if the special bag got ripped).
The other thing I can easily imagine is that a werewolf might have a special "transformation den" hidden in the woods not too far from the house. A little underground room with a hidden entrance, someplace warm and dry where you could crawl in, transform, and dress, without the risk of being seen entering, leaving, or hanging about your home in gestalt or wolf form.
Should have something around for emergencys or whatever.
