Grapevines are rated according to their hardiness: here in Missouri most of the grapevines we grow are rated for cold weather and can survive winters with temperatures below zero.
 
While lately it's been cold, really cold, we have not had extremely rapid fluctuations in the temperature (extreme cold to warm and back again to frigid) which is what harms the vines. For the most part, the hardy hybrid and native American varieties of grapes that grow throughout Missouri are able to handle the low temperatures that Mother Nature throws at us, however, areas that experienced lows of -11 degrees F or lower may see some bud injury. At this point it will probably be early spring before vine damage, if there is any, is evident.