Vineyardists know this, but for those of you not viticulturally inclined: the significance of two weeks of summer in the middle of winter is twofold:
Should that January warm spell cause bud break to advance two weeks, that is not good news for inland valleys or low lying areas. The reason is that late spring frosts are not uncommon in these lower lying areas, and if bud break is moved up two weeks, those buds/ blooms are more susceptible to a late spring freeze.
Contrarily, if the warm January followed by warm spring days (but standard cold nites) causes bud break to be retarded for several weeks, that could conceivably delay ripening by two weeks, which could then cause hanging grapes to be subject to early fall frosts. Which way the bizarre January weather is going to affect things, I don't have a clue. But it will affect either an early bloom with potential for late spring frost damage, or it will affect a late harvest with early fall frost damage to grapes. The optimist in me says neither of these will happen. The realist says it probably will, one way or the other.