If I recall... he sucks in this kind of weather... at least in his old age he does...
Actually, to the contrary, Favre holds a huge advantage when the weather gets ultra cold or if the conditions are cold and wet. Most people's thoughts on that subject are clouded by his last performance vs. the Giants in the NFC Conference Championship last season. And yes, he did look cold and miserable in that game and threw a costly pick to end the game.
But over the years he always outperformed his competition in the cold and wet conditions. They used to keep a Favre stat with his record when the temp was below 35 degrees or something like that and it was something insane like 18~2 (I'd have to look it up). Being in Green Bay his entire career he not only had to get used to the cold, but had to actually embrace the idea of acting immune to it while your opponents shivered and complained. Physically, Favre has extremely large hands and has always been able to maintain control better than others in the same conditions.
That's not to say that his NYJ receivers know how to catch the ball in the cold, and that there won't be drops. But Favre will be fine unless he takes needless chances forcing things into coverage.