The Packers are known as a dome team this year. There could conceivably be a drop in their longer pass plays, but the Packers actually have less explosive plays then you'd expect. They love going to Finley over the middle, to Jennings on the seam, and Nelson on the out route. cold weather alone (without slick conditions or strong wind) won't affect those plays much.
The Giants have the fewest rushing yards per game this season (89.2), but the Packers have an inordinately hard time with bigger backs (think Legarette Blount earlier this season) so they'll run the ball pretty well. But playing at Lambeau in the playoffs is crazy. The crowd is so loud when the opposing team is on offense that they could bungle multiple plays (especially with audibles) and so disciplined and quiet when the Packers put together their drives. Weather/stadium conditions favor the Packers overall.