I think that the significance of Proctor using the reference of "winter" is to describe the emotional climate between he and his wife at the start of the drama. It is Miller's genius to reveal how difficult it is for a married couple to persevere through fundamental challenges. In this case, Proctor's affair with Abigail has rocked the marriage to its very core. Its fundamental essence has been brought into question through the affair. Both of them are nursing their own form of hurt, both at themselves and at the other, in the start of Act II. Innocuous actions are seen in different lights given the emotional climate and timbre of the couple at this point. In Proctor's bringing out "winter," it helps to illuminate the coldness that Elizabeth is showing towards her husband. It is also reflective of the fact that their marriage is in trouble. When Proctor adds spice to the broth that is simmering, it helps to bring out how their marriage, in general, is in need of some additives. The coldness and emotional complexity that the affair revealed is where Proctor's comment is directed. Miller recognizes this emotional dynamic in the couple trying to rebuild their relationship and their life together. It is in this context, one of emotional frailty, difficulty, and hurt, where the reference to seasonal change, in particular one of barrenness and coldness, is so telling and relevant.