If it's pouring rain and soak the leather,I think it will damage it just like any other leather. You will get water stains but it will "blend" in eventually when you it gets patina.
What happens to the leather when it gets soaked? Sorry, I'm not used to owning leather products.
Like any other leather products, it will get damaged and stinks..
It's bound to get some water stains eventually like 'bagsnbags' says 'it will "blend" in'. Just gently dap off any excess moisture and it will be fine. It really does wear well as time goes on the vachetta will turn a light honey patina. You'll probably love your leather products even more.