As far as I know, all of his major and not-so major GOP opponents are there, as are Bernie and Hillary. If road hazards were really an issue, he could cancel the rally, but you’re not going to deny that not even being in the state doesn’t look like a sign of commitment to potential supporters (i.e. “if he can’t even be bothered to be here like the other candidates, why should we trudge through the snow to vote for him?”)
You know what? NH voters get it that anyone who could get out of the area that got slammed without much warning is providing a service.
Why would he sit around in NH being unproductive when he could take the time to rally in another important state??