The main drawback to visiting in the winter is many of the roads close for the season. Primary roads, such as Highway 441, Cades Cove Road Loop and Little River Road remain open, weather permitting. But, secondary roads close through the winter, you can look at the full list of seasonal road closures here. Clingmans Dome Road closes to vehicle traffic from December 1st to March 31st. Because it is the highest elevation in the park, and can experience temperature differences of 10-20° from the bottom of the mountain to it’s top. (But, just because the road is closed doesn’t mean you can’t still get to the top for amazing views. You can hike on the Appalachian Trail from Newfound Gap to the top of Clingmans Dome. This 15-mile hike will take you to the tallest peak in the park, giving you outstanding views of the Smokies; and when the air quality is high, you can see into seven states!)
Another drawback to visiting the Smokies in the winter is the unpredictable precipitation. On average, per year, the lower elevations experience 55 inches of rainfall, and higher elevations could see as much as 85 inches of rainfall. Sometimes the temperature is not cold enough to turn that precipitation into snow, so you get a cold, wet rain in the winter—which most people don’t find ideal for hiking. Always have rain gear with you, in case the weather changes drastically, as it often does.