The first of many cold days are already upon Siouxlanders and it only goes downhill from here. In November, the average high temperature in Sioux City is 46 degrees, in December it is 32 degrees and last January the temperature dropped to as low as 4 degrees. When it gets that cold, anywhere you can insulate your home, i.e., windows and doors, helps. An insulated garage door can also help keep your home cozy, especially if your garage is attached to your home. But, it has other benefits as well.