Are they Summer bearers ( floricanes) or Autumn bearers ( primo canes) wisgardener?
The summer bearers grow their fruit on canes that have grown the previous summer. So you must leave the newly grown canes over winter and they are tied to some form of support and these give you your fruit in the early to mid summer in one large 'flush'.
The canes that have already cropped are removed ...so any time you can get at them, cut them out at ground level.
Autumn cropping rasps( the primo canes) crop on canes that grow the same year. These plants can be cut down to ground level completely each year. ( if you wish a few canes can be left to give a few earlier berries.)
So..again if you can get at the bases of the plants, prune when you can.
I would add that snow acts as a great insolater for the roots...therefore it may be best if you leave the pruning now until the thaw takes place ...nothing will be going on below ground anyway.
But..if you have the summer bearers it would pay to make sure the canes needed for next year are tied to a support system as they could be damaged by snow and wind during the worst of the winter.