I'm bumping this so others can respond as I know they will want to. If it was me, I'd call a rescue or shelter and explain the problem. Just make sure that they aren't going to euthanize the dog. I'm not sure how old he is, but this can be a serious concern with older, "unadoptable" dogs. Can you take him? Do you know this neighbor? Can you ask them if they would be willing to sell/give you the dog? Poor little thing....
If all else fails, call the police. It's inhumane to leave him out there all day, especially if the temperature is dropping to 37F.
