In extremely cold climates, it is often necessary to change weather stripping every year. People seem to think that once stripping is installed, it will work well for years to come. This is not the case. However, even if the weather stripping for the door is new, and in good shape, the cold weather may warp the door slightly, in which case the existing stripping needs to be adjusted. The cold air that is coming through the door may be only in one specific part of the door. There are two ways to find out. Close the door on a piece of paper. If you can pull the paper out there is little or no protection in that area. If the paper is stuck and you cannot pull it out, the stripping is doing the job. Try moving the paper along the edges of the door until you find the warped area. Or you can open a window on the other side of the house and hold a cigarette or incense up to the door. The forced draft will indicate where the problem is by drawing the smoke through the door. Loosen the screws to adjust the weather stripping and repeat either method until the draft is eliminated.