It drives Dave CRAZY when the dogs pee on the deck when there is snow on it. ...and all three of them will do it. They would never even THINK about peeing there if there was no snow, so it has to be that, in their little minds, "snow means go".
It doesn't bother me if she pees on a pile of snow on the deck. I figure it'll just get all diluted when it melts and run through the spaces between the deck boards. Plus, when our snow melts, it usually is because of rain and that helps wash it away.