Aww he looks hug-able even when dirty! lol so cute, My dog tanner is the same way, The rain/snow doesnt seem to bother him a bit. I call him my eeyore cuz he will jus sit out in the rain, and of course because i love eeyore!
Thankfully, it's only his topcoat that gets dirty. He likes getting rubbed down with a moist towel and he eventually he dries and the leftover dirt falls out. Days like this one require some brushing to get the big chunks out and keep him from getting matted.