Long as their white they'll be allright. Sound's dumb,, but long as the snow isn't melting on the cows and their covered with white snow they're insulated enough and fat enough to be ok.   The one's to really worry about are the wet one's moving real slow and shivering more than they should be for the weather their in.

Cold rain is worse than plain ol' cold or cold snow any day. Warmer weather breeds with not much guard hairs had a hard time in the cold rain.  The only thing worse is cold rain and wind....

Don't envy you keeping them warm enough.