Gatlinburg has really turned into a four season destination. Everyone has their favorite time to visit.
In the Spring, you have beautiful wildflowers blooming and all of the foliage is coming alive, everything is bright green. The animals are coming out from their winter naps or coming back from warmer climates. The weather in the Spring is usually in the upper 40s in the morning and 60s by the afternoon. Of course you can expect plenty of rain. The crowds and traffic are lighter and you can usually find better rates at Bed and Breakfasts, Cabins, and Hotels.
Summertime is a favorite time to vist for may because you have hot days, perfect for tubing, white water rafting, or exploring the higher elevations in the Smoky Mountains where the temps stay cooler. The summertime temps are usually in the mid to upper 80s, breaking 90 every now and then. Downtown is hopping with tons of activity and large crowds. Of course don't forget about 4th of July parades, fireworks, barbeques, fishing, and everything else that make summer great!!
Fall is the busiest time of year in Gatlinburg. The leaves are all changing color and giving a spectacular show. This show starts in the higher elevations around 5000 feet in early October and continues all the way into the valleys in Mid-November. This is a perfect time to get a good local map and find some backroad to avoid all of the traffic. You also have several craft fairs and mountain music festivals. If you want to find some solitude just walk onto one of the "quiet walkways" in the Smoky Mountain National Park. If you are trying to find that perfect Bed and Breakfast you should book early because they fill up fast!
In the Winter the mountains take on a different look, and for many people this is thier favorite time to visit. The weather is cold, but not bitter cold like our northern states. The daytime average is in the mid 40s and it will dip into the 20s at night. It snows occasionally in the town, but it rarely stays for more than a few hours. Just 500 feet up the mountain the snow is likely to last much longer, and the Ober Gatlinburg Ski resort stays open all winter. The town reverts back to its small town roots. You can actually park on Main Street and walk in the shops and restaraunts.