Please go over to the 2011 hops garden thread and notice my post on page 5, second post.
My shoots were already exposed and the snow was extremely wet for a day then completely frozen the next. Now everything is going gangbusters.
With hops it is one of those RDWHAHB situations. Everything is fine. Especially since yours are just rhizomes. If anything the water might help. You don't even need mulch at this point unless it is very dry.