Bad/slippery field conditions probably don't impact the Bears much at all, since they get to play their home games on the worst playing surface in the NFL every year.
I do think the cold temps could impact Williams/Bears throwing the ball more than Love, particularly with his ability to escape the pocket and make plays with his feet. Williams has alot of juke to his scrambling, and that quick twitch stuff just isn't as dynamic in cold weather on a grass outdoor surface. Getting Walker back and keeping the Bears from a run-heavy game plan will go a long way to putting the Bears team in their place after the 2 month horseshoe they've been riding with. Williams will throw the Packers a couple of picks if DBs can catch the ball, or I can see a strip sack at a big moment turning the game with Williams trying to do too much. Someone other than Parsons is going to have a big game rushing the passer/blitzing, and having Cooper or Walker availably to shadow Williams is big if they can get the Bears into 3rd and longs/1-dimensional passing.
If the Packers take care of the football, they're going to win Sunday afternoon. The Bears as a team have gotten way too much favorable press leading up to and especially right after beating an inconsistent Eagles team, something Chicago hasn't dealt with since most of their roster has been born, and that's a recipe for a clunker going on the road for a team that is very new to success. I know Chicago might get some of their early season secondary starters back on defense, but they are among the league's worst run defenses and I think GB is going to make some hay on the ground and with play action.